Search

In this study fixed-target spectra obtained by the Chicago-Princeton (C-P) collaboration at Fermilab in the mid seventies are analyzed with a two-component spectrum model (TCM) that has been applied successfully to a number of collision systems at the RHIC and LHC in the past. It is from C-P data that the Cronin effect was first inferred. TCM analysis leads to factorization of collision-energy and target A dependences. Over the energy range of C-P data energy dependence is restricted to model-function shapes on $p_t$ whereas A dependence is restricted to particle densities for three hadron species and their antiparticles. A dependence for soft and hard components varying separately as power laws $A^{\alpha_s}$ and $A^{\alpha_h}$ with fixed exponents is a central finding of this study. The trends $A^{\alpha(p_t)}$ inferred by the C-P collaboration resulted from treating spectra as monolithic which confuses the distinct $p_t$ (model functions) and A (particle densities) dependences. The Cronin effect resulting from that confusion is easily explained in a TCM context. Power-law trends for pions at 25 GeV are quantitatively compatible with trends at LHC energies. The relation of exponents $a_s$ and $a_h$ to $p$-A centrality is examined in detail. A Glauber model of $p$-A centrality seems invalid., Comment: 22 pages, 25 figures

In recent years certain experimental results from small collision systems (e.g. p-p, d-Au, p-Pb) at the RHIC and LHC have been reinterpreted as evidence for formation therein of a dense flowing medium (QGP) despite small collision volumes. Systems that had been assigned as simple references (e.g. cold nuclear matter) for larger A-A collisions would then no longer play that role. This presentation examines conventional interpretations of certain data features in the context of a two-component (soft+hard) collision model. Specific topics include centrality determination for p-Pb collisions, interpretation (or not) of nuclear modification factors, significance of claims for strangeness enhancement, and interpretation of the "ridge" in p-p collisions. For p-p and p-Pb data analysis results indicate that p-Pb collisions are simple linear superpositions of p-N collisions, and N-N collisions within small systems generally follow simple and consistent rules. However, there is more to be learned about "basic" QCD in small systems with improved analysis methods., Comment: 9 pages, 16 figures, Proceedings: New Trends in High Energy Physics

A parametrized mathematical model is required to extract the information carried by transverse momentum $p_t$ spectra from high-energy nuclear collisions and subject it to physical interpretation in terms of possible hadron production mechanisms. The importance of proper model construction and implementation has increased with the emergence of claims for ``collectivity'' (flows) associated with small collision systems (e.g. $p$-$p$ and $p$-Pb). A two-element spectrum model, denoted herein as the Bylinkin model, includes an exponential element and a ``power-law'' element interpreted by the authors to represent emission from a thermalized source and from jet production respectively. Application of the Bylinkin model to various collision systems has led to conclusions about achievement of thermalization and other characteristics of nuclear dynamics. In connection with the Bylinkin model there has emerged theoretical conjecture that the thermalization mechanism signaled by the exponential element is hard processes interacting with quantum entanglement within projectile protons. Predating the Bylinkin model is a two-component (soft+hard) model (TCM) derived empirically from the evolution of $p$-$p$ spectrum data with event multiplicity as a form of data compression. The TCM has been applied to many collision systems and hadron species from which a systematic description of high-energy nuclear collisions has emerged. The Bylinkin model can be seen as a limiting case of the TCM model functions that is unsuited to represent underlying production mechanisms. The present study provides detailed comparisons of the two models for a variety of situations and contrasts two very different data interpretations that result., Comment: 22 pages, 17 figures

Nuclear modification factors (NMFs) applied to A-B collision systems consist of $p_t$ spectrum ratios rescaled by an estimated number of nucleon-nucleon binary collisions. Interest in NMFs is motivated by possible modification (suppression?) of jet production in more-central A-B collisions conjectured to arise from a deconfined quark-gluon plasma or QGP. Interpretation of NMFs is complicated by the so-called Cronin effect wherein similar ratios derived from fixed-target p-A data exhibited suppression at lower $p_t$ and enhancement at higher $p_t$ with increasing atomic weight A. This presentation describes precision analysis of identified-hadron spectra from 5 TeV $p$-Pb collisions that accurately isolates the entire jet contribution. Evolution of NMF spectrum ratios with $p$-Pb centrality is interpreted in terms of variation of corresponding jet contributions to spectra. The same method is then applied to Chicago-Princeton fixed-target spectrum data from the seventies wherein the Cronin effect was first observed. Soft and hard particle densities vary as fixed powers of $A$. Inferred jet contributions are quantitatively consistent with extrapolation from higher energies. The Cronin effect is a simple result of rescaling particle-density spectra by factor $1/A^{1/3}$., Comment: 15 pages, 8 figures, Proceedings of ISMD 2023

Nuclear modification factors (NMFs) are spectrum ratios rescaled by an estimate of the number of binary N-N collisions $N_{bin}$ within an A-B collision. NMFs from more-central A-A collisions have been interpreted to indicate formation of a quark-gluon plasma (QGP) when compared with results from control $p$-A or $d$-A collisions. However, subsequent analyses of such control systems are now also interpreted to indicate QGP formation, calling into question proper interpretation of NMFs. An additional complication is the nature of the so-called ``Cronin effect'' contribution to NMF structure that is not well understood. In the present study a two-component model of hadron production (TCM) is applied to identified-hadron (PID) $p_t$ spectra from 5 GeV $p$-Pb collisions extending up to 20 GeV/c. Hard components (jet fragment distributions) are accurately isolated and their evolution with collision centrality parametrized. The TCM is then applied to NMFs without rescaling by $N_{bin}$, allowing direct comparisons between NMF evolution and hard-component evolution with centrality. To address the Cronin effect the TCM is applied to fixed-target $p$-A spectra from the Chicago-Princeton (C-P) collaboration, the origin of the Cronin effect. Inferred C-P spectrum hard components are quantitatively consistent with extrapolation of jet-related structure from higher energies. As a general conclusion spectrum ratios such as NMFs are difficult to interpret, whereas direct differential analysis of isolated spectra may be interpreted simply and accurately., Comment: 24 pages, 23 figures, updated Sec. VII includes additional information

Small collision systems, e.g. $p$-$p$ and $p$-Pb collisions, comprise a potential reference for more-central A-A collisions with regard to production (or not) of a thermalized quark-gluon plasma (QGP). Small systems with low particle densities should evolve according to simple QCD mechanisms including projectile-nucleon dissociation and dijet production. But it is now claimed that QGP may appear even in $p$-$p$ collisions based on apparent evidence for radial flow from shape evolution of $p_t$ spectra and from variation of total yields for strange and multistrange hadrons relative to statistical models. The present study confronts such arguments with a detailed analysis of $p_t$ spectra for strange and multistrange hadrons from 5 TeV $p$-Pb collisions and 13 TeV $p$-$p$ collisions via a two-component model (TCM) of hadron production. Based on previous analysis of lighter hadrons the TCM accurately predicts spectra for Cascade and Omega hadrons. Significant results include multistrange hadron spectra dominated by jet fragments, variation of strange-hadron abundances exaggerated by certain plot formats and spectrum extrapolations, and detailed relations between ensemble-mean $\bar p_t$ evolution with event charge density and small shifts of jet fragment distributions on $p_t$. Within the context of the TCM, $p$-$p$ and $p$-Pb collision systems with comparable jet contributions are found to be equivalent within data uncertainties. Attribution of certain data features to radial flow is falsified., Comment: 21 pages, 13 figures

In previous analyses a two-component (soft+hard) model (TCM) was developed for identified-hadron (PID) spectra from 5 TeV $p$-Pb and 13 TeV $p$-$p$ collisions. Spectrum data are generally described within their statistical uncertainties. Within the model are coefficients $z_{si}(n_s)$ and $z_{hi}(n_s)$ that denote the fractions of hadron species $i$ within total soft $\bar \rho_s$ and hard $\bar \rho_h$ charge densities and that vary significantly with event index $n_s = \Delta \eta \bar \rho_s$. This letter reports that variation of those coefficients with $n_s$ implies transport of hadron species from soft component to hard component, increasingly with increased jet production, while conserving the total particle number for each species that is predicted by a statistical model. The extent of transport is simply proportional to hadron mass., Comment: 4 pages, 3 figures

Identified-hadron (PID) $p_t$ spectra from 13 TeV $p$-$p$ collisions are compared with a two-component (soft+hard) model (TCM) that accurately distinguishes jet-related hadron production (hard component) from nonjet projectile-nucleon dissociation (soft component). The present $p$-$p$ study is similar to and is guided by recent TCM studies of PID spectra from 5 TeV $p$-Pb collisions. The combined analyses serve to establish a well-understood quantitative description of PID hadron production in small collision systems as a control experiment. The control can then be contrasted with conventional interpretations of collision data from more-central A-A collisions as indicating formation of a quark-gluon plasma (QGP). PID $p_t$ spectra from 13 TeV $p$-$p$ collisions exhibit simple consistency with spectra from 5 TeV $p$-Pb collisions. Hadron species abundances are consistent with statistical-model trends predicted prior to commencement of the large hadron collider program. Differential spectrum structure and various ratio measures are quantitatively explained by the TCM, including its jet contribution, and admit no room for claims of hydrodynamic flows in small collision systems., Comment: 23 pages, 23 figures

The blast-wave (BW) spectrum model has been applied extensively to nucleus-nucleus collision data with the intention to demonstrate formation of a quark-gluon plasma (QGP) in more-central A-A collisions. More recently the BW model has been applied to p-p, d-Au and p-Pb collisions. Such results are interpreted to indicate that ``collectivity'' (flows) and QGP appear in smaller systems. I consider variations of the BW model and supporting assumptions. In this talk I review BW analysis of identified-hadron spectra from 5 TeV p-Pb collisions and examine the shape evolution of model spectra with collision centrality. I evaluate data-model fit quality using conventional statistical measures. I conclude that the BW model is not a valid data model., Comment: 6 pages, 7 figures

The blast-wave (BW) spectrum model is interpreted to reveal relativistic motion (collective flow) of the hadron emission system relative to the center-of-momentum (CM) frame in high-energy A-B collisions. In essence, any spectrum deviation in the CM frame from a reference distribution (e.g. Boltzmann distribution on transverse mass $m_t$) is interpreted to reveal a flowing particle source. The ALICE collaboration has applied the BW model to identified hadron (PID) spectra for four hadron species from 5 TeV $p$-Pb collisions. From model fits BW parameters $T_{kin}$ (freeze-out temperature) and $\langle \beta_t \rangle$ (transverse speed) are inferred that suggest strong radial expansion in more-central $p$-Pb collisions. Such results from the small $p$-Pb collision system are counterintuitive given that strong radial expansion should be driven by large density gradients. The present study is intended to address that problem. Several methods are employed to evaluate the quality of the BW model data description, including logarithmic derivatives and the Z-score statistic. The stability of the BW model definition across several applications to data is investigated. The BW model data description is compare to that of the two-component (soft+hard) model (TCM) that has been previously applied to the same $p$-Pb PID spectra. The general conclusion is that the BW model is falsified by $p$-Pb PID spectrum data according to standard statistical measures and that the fitted parameter values do not convey the intended meaning. Statistically acceptable data descriptions provided by the TCM indicate that other collision mechanisms (projectile-nucleon dissociation, dijet production), that are consistent with conventional QCD, are more likely responsible for observed spectrum characteristics., Comment: 26 pages, 20 figures

This is the second part of a two-part article on precision modeling of identified-hadron (PID) $p_t$ spectra from 5 TeV $p$-Pb collisions. In Part I a revised two-component (soft + hard) model (TCM) of PID spectra was introduced, an apparent detection inefficiency for protons was corrected and jet-related spectrum hard components isolated via an improved method were compared to a fixed TCM serving as reference. In the present article (Part II) the TCM is further elaborated to describe centrality variation of spectrum hard components (and therefore entire spectra) within data statistical uncertainties as determined by a standard statistical measure (Z-scores). The completed PID TCM is then used to investigate properties of spectrum and yield ratios (e.g. $p/\pi$ ratios) and ensemble-mean $\bar p_t$ data. Systematic differences are observed between meson and baryon hard components. With increasing $p$-Pb centrality meson hard components shift to lower $p_t$ while baryon hard components shift to higher $p_t$. Those trends explain quantitatively the main features and centrality variation of spectrum ratios. Ensemble-mean $\bar p_t$ trends are also predicted at the level of data statistical uncertainties, and details of the $\bar p_t$ centrality trends are explained quantitatively., Comment: 19 pages, 14 figures

The ALICE collaboration recently reported high-statistics $\bf p_t$ spectra from 5 TeV and 13 TeV p-p collisions with intent to determine the role of jets in high-multiplicity collisions. In the present study a two-component (soft + hard) model (TCM) of hadron production in p-p collisions is applied to ALICE $\bf p_t$ spectra. As in previous TCM studies of A-B collision systems jet and nonjet contributions to $\bf p_t$ spectra are accurately separated over the entire $\bf p_t$ acceptance. The statistical significance of data-model differences is established leading to insights concerning selection bias and spectrum model validity., Comment: 5 pages, 6 figures

In a recent analysis of high-statistics $p_t$ spectra from 5 and 13 TeV $p$-$p$ collisions a two-component (soft+hard) model (TCM) of hadron production near midrapidity, based on fixed model functions independent of collision multiplicity $n_{ch}$ or event selection criteria, was employed as a reference to determine data biases induced by the selection criteria. As in previous studies the fixed TCM accurately isolated jet-related and nonjet contributions to spectra. It was observed that two selection criteria (V0M and SPD), based on different pseudorapidity $\eta$ acceptances, bias the spectrum hard component (jet fragment distribution) in different but complementary ways whereas the soft component is not significantly biased. In the present study TCM model functions are adjusted (i.e. fitted) to accommodate data. The effect of selection bias is then represented by smooth evolution of model parameters with $n_{ch}$. To evaluate the quality of model fits, Z-scores (data-model differences divided by statistical uncertainties) are evaluated and compared with data/model ratios that are often used for such comparisons. Based on Z-scores the variable TCM is compared with two other frequently-invoked models: the Tsallis model and the blast-wave model as they have been recently applied to the same spectrum data. The results are relevant to recent claims that collectivity (various flow manifestations) as a possible manifestation of QGP formation is observed in small systems. Data systematics suggest that these $p$-$p$ $p_t$ spectra are consistent with conventional QCD., Comment: 17 pages, 15 figures

The ALICE collaboration at the large hadron collider (LHC) recently reported high-statistics $p_t$ spectrum data from 5 TeV and 13 TeV $p$-$p$ collisions. Particle data for each energy were partitioned into event classes based on the total yields within two disjoint pseudorapidity $\eta$ intervals denoted by acronyms V0M and SPD. For each energy the spectra resulting from the two selection methods were then compared to a minimum-bias INEL $> 0$ average over the entire event population. The nominal goal was determination of the role of jets in high-multiplicity $p$-$p$ collisions and especially the jet contribution to the low-$p_t$ parts of spectra. A related motivation was response to recent claims of "collective" behavior and other nominal indicators of quark-gluon plasma (QGP) formation in small collision systems. In the present study a two-component (soft + hard) model (TCM) of hadron production in $p$-$p$ collisions is applied to the ALICE spectrum data. As in previous TCM studies of a variety of A-B collision systems the jet and nonjet contributions to $p$-$p$ spectra are accurately separated over the entire $p_t$ acceptance. Distinction is maintained among spectrum normalizations, jet contributions to spectra and systematic biases resulting from V0M and SPD event selection. The statistical significance of data-model differences is established. The effect of {\em spherocity} (azimuthal asymmetry measure nominally sensitive to jet production) on ensemble-mean $p_t$ vs event multiplicity $n_{ch}$ is investigated and found to have little relation to jet production. The general results of the TCM analysis are as expected from a conventional QCD description of jet production in $p$-$p$ collisions., Comment: 22 pages, 20 figures

Identified-hadron (PID) spectra from 2.76 TeV Pb-Pb and $p$-$p$ collisions are analyzed via a two-component (soft + hard) model (TCM) of hadron production in high-energy nuclear collisions. The PID TCM is adapted with minor changes from a recent analysis of PID hadron spectra from 5 TeV $p$-Pb collisions. Results from LHC data are compared with a PID TCM for 200 GeV Au-Au pion and proton spectra. 2.76 TeV proton spectra exhibit strong inefficiencies above 1 GeV/c estimated by comparing the $p$-$p$ spectrum with the corresponding TCM. After inefficiency correction Pb-Pb proton spectra are very similar to Au-Au proton spectra. PID A-A spectra are generally inconsistent with radial flow. Jet-related Pb-Pb and Au-Au spectrum hard components exhibit strong suppression at higher $p_t$ in more-central collisions corresponding to results from spectrum ratio $R_{AA}$ but also, for pions and kaons, exhibit dramatic enhancements below $p_t = 1$ GeV/c that are concealed by $R_{AA}$. In contrast, enhancements of proton hard components appear only above 1 GeV/c suggesting that the baryon/meson "puzzle" is a jet phenomenon. Modification of spectrum hard components in more-central A-A collisions is consistent with increased gluon splitting during jet formation but with approximate conservation of leading-parton energy within a jet via the lower-$p_t$ enhancements., Comment: 25 pages, 19 figures

The journal Nature recently published a letter titled "Creating small circular, elliptical, and triangular droplets of quark-gluon plasma" [1]. The basis for that claim is a combination of measured Fourier amplitudes $v_2$ and $v_3$ from collision systems $p$-Au, $d$-Au and $h$-Au (helion $h$ is the nucleus of atom $^3$He), Glauber Monte Carlo estimates of initial-state transverse collision geometries for those systems and hydro Monte Carlo descriptions of the $v_n$ data. Correspondence between hydro $v_n$ trends and data trends is interpreted as confirmation of "collectivity" occurring in the small collision systems, further interpreted to indicate QGP formation. QGP formation in small systems runs counter to pre-RHIC theoretical assumptions that QGP formation should require large collision systems (e.g. central A-A collisions). There is currently available a broad context of experimental data from $p$-$p$, A-A and $p$-Pb collisions at the RHIC and LHC against which the validity of the Nature letter claims may be evaluated. This talk provides a summary of such results and their implications. [1] Nature Phys. 15, no. 3, 214 (2019).}, Comment: 6 pages, 6 figures, Proceedings of XLIX International Symposium on Multiparticle Dynamics (ISMD 2019)

A recent letter published in the journal Nature reports observation at the relativistic heavy ion collider (RHIC) of quark-gluon plasma (QGP) formation in small asymmetric collision systems denoted as $p$-Au, $d$-Au and $^3$He-Au. The claimed phenomenon, described as `short-lived QGP droplets,' is inferred from a combination of Glauber Monte Carlo simulations, measurement of two azimuth Fourier amplitudes $v_2$ and $v_3$ and hydro theory calculations. While that claim follows a trend in recent years to report `signals' conventionally attributed to QGP as appearing also in smaller collision systems, the new result remains surprising in the context of expectations before first RHIC operation that small systems, e.g. $d$-Au collisions, would provide control experiments in which a QGP was unlikely to appear. An alternative interpretation of the recent RHIC result is that small-system control experiments do convey an important message: The `signals' conventionally attributed to QGP formation in larger A-A collisions do not actually represent that phenomenon in any system. The present study reviews a broad array of experimental evidence for or against QGP formation in several collision systems. It examines in particular hydro theory descriptions of spectra and correlations usually interpreted to support QGP formation. Available evidence suggests that data features conventionally attributed to QGP formation represent either minimum-bias jet production or a nonjet azimuth quadrupole with properties inconsistent with a hydro hypothesis., Comment: 26 pages, 19 figures, four figures updated

In preparation for the heavy ion program at the relativistic heavy ion collider (RHIC) $d$-Au collisions were designated as a control experiment for possible discovery of a quark-gluon plasma (QGP) in more-central Au-Au collisions, and contrasting results from the two systems seemed to support such a discovery. In contrast, recent results ($p_t$-spectrum and angular-correlation features) from $p$-Pb collisions at the large hadron collider (LHC) have been interpreted to support claims of hydrodynamic flows and QGP formation even in small collision systems. The present study addresses such claims via a two-component (soft + hard) model (TCM) of identified-hadron (PID) $p_t$ spectra from 5 TeV $p$-Pb collisions. $p$-Pb centrality is adopted from a previous study of ensemble-mean $\bar p_t$ data from the same system. $p$-Pb $p_t$ spectra for pions, kaons, protons and Lambdas are described by the TCM within their point-to-point uncertainties. Invariance of the TCM hard component vs $p$-Pb centrality indicates that jet formation remains unchanged in $p$-Pb collisions relative to $p$-$p$ collisions, and radial-flow contributions to spectra are negligible. These $p$-Pb TCM results have implications for interpretation of similar data features from A-A collisions in terms of QGP formation., Comment: 20 pages, 10 figures, updated to published version

The PYTHIA Monte Carlo (PMC) has been applied broadly to simulations of high-energy $p$-$p$ and $p$-$\bar p$ collisions. The PMC is based on several assumptions, such as that most hadrons result from jet production (multiple parton interactions or MPIs), that $p$-$p$ centrality is relevant and that color reconnection (CR) strongly influences fragmentation to jets. An alternative description is provided by the two-component (soft + hard) model (TCM) of hadron production. TCM analysis of $p$-Pb ensemble-mean-$p_t$ data reveals centrality trends quite different from those estimated via a geometric Glauber model based on the eikonal approximation. Glauber estimates of binary-collision number are three times TCM estimates. Detailed study of $p$-Pb data conflicts with a basic Glauber assumption -- that a projectile proton may interact simultaneously with multiple target nucleons. Instead, in both $p$-$p$ and $p$-A collisions, a $p$-N collision once initiated is exclusive of other possible interactions (during that collision), and within the collision any pair of participant partons may interact -- a $p$-N collision is thus "all or nothing." In this presentation the PMC is challenged by an assortment of contradictory data, and evidence for $p$-N exclusivity is reviewed to make a case for the "preoccupied proton" of the title., Comment: 10 pages, 7 figures, Proceedings of XLVIII International Symposium on Multiparticle Dynamics

The PYTHIA Monte Carlo (PMC), first introduced more than thirty years ago, remains a popular simulation tool both for analysis of $p$-$p$ collision dynamics and for detector design and calibration. The PMC assumes that almost all produced hadrons result from parton-parton scatterings (interactions) described by pQCD (a hard component), and that multiple parton interactions per collision event (MPIs) are a common occurrence. In contrast, a two-component (soft + hard) model (TCM) of high-energy collisions, inferred inductively from a variety of data formats, attributes a majority of final-state hadrons to a soft component (projectile-nucleon dissociation) and a minority to a hard component representing minimum-bias dijet production (corresponding to measured jet spectra and fragmentation functions). The hard-component hadron yield is precisely proportional to the square of the soft-component yield over an interval corresponding to 100-fold increase in dijet production. The two data descriptions appear to be in conflict. This study presents a detailed comparison of the two models and their relations to a broad array of collision data. The PMC appears to disagree with some data, whereas the TCM provides an accurate and comprehensive data description., Comment: 24 pages, 15 figures. arXiv admin note: text overlap with arXiv:1706.02166, arXiv:hep-ph/0402078 by other authors

A geometric Glauber model applied to p-p or p-A collisions assumes that participant partons within a projectile nucleon independently follow eikonal trajectories, just as for projectile nucleons within target nuclei, and interact independently with any target nucleons encountered along their trajectory. A noneikonal quadratic relation for dijet production observed for p-p collisions suggests that such assumptions for p-N collisions may be incorrect. Data from p-A collisions supports that conclusion. For both isolated p-p collisions and for p-N interactions within p-A collisions a proton projectile interacts with only a single target nucleon within a brief time interval. Multiple overlapping p-N collisions are inhibited, suggesting the exclusivity of p-N interactions within p-A collisions., Comment: 5 pages, 5 figures

A recent study of 5 TeV $p$-Pb centrality combined a Glauber model of $p$-Pb collision geometry with an assumption of linear scaling between $n_{ch}$ (charge) integrated within some $\eta$ acceptance and the number of nucleon participants $N_{part}$. The study concluded that $N_{part}$ increases to nearly 16 in central collisions, and the high-$p_t$ region of $p$-Pb $p_t$ spectra rescaled by the Glauber-estimated number of $p$-N binary collisions remains consistent with a $p$-$p$ spectrum for the same energy, independent of $p$-Pb centrality. However, the relation between $N_{part}$ and $n_{ch}$ derived from a two-component (soft + hard) model (TCM) study of ensemble-mean $\bar p_t$ data for the same system is quite different. This article reports a detailed analysis of the Glauber study and the question of centrality in $p$-A collisions. The Glauber centrality model is compared with the $\bar p_t$ TCM to understand the sources of major differences. The assumption of linear proportionality between $n_{ch}$ and $N_{part}$ is found to be inconsistent with $\bar p_t$ data. Properties of the convolution integral relating a differential cross section and hadron production model to an event distribution on $n_{ch}$ are examined. An alternative differential-cross-section distribution is inferred from charge-multiplicity data, and the upper limit on $N_{part}$ is estimated to be near 8. The TCM centrality model is then applied to $p_t$ spectrum ratios to predict results for $p$-Pb spectra. The spectrum TCM is tested with identified-pion spectra from 5 TeV $p$-Pb collisions and the result is consistent with previous $p$-$p$ TCM results. A TCM prediction that the spectrum ratio at high $p_t$ should increase to 14 for central $p$-Pb collisions due to quadratic dependence of dijet production on $n_{ch}$ is consistent with $\bar p_t$ data from the same system., Comment: 24 pages, 25 figures

Collectivity, as interpreted to mean flow of a dense medium in high-energy A-A collisions described by hydrodynamics, has been attributed to smaller collision systems -- p-A and even p-p collisions -- based on recent analysis of LHC data. However, alternative methods reveal that some data features attributed to flows are actually manifestations of minimum-bias (MB) jets. In this presentation I review the differential structure of single-particle $p_t$ spectra from SPS to LHC energies in the context of a two-component (soft + hard) model (TCM) of hadron production. I relate the spectrum hard component to measured properties of isolated jets. I use the spectrum TCM to predict accurately the systematics of ensemble-mean $\bar p_t$ in p-p, p-A and A-A collision systems over a large energy interval. Detailed comparisons of the TCM with spectrum and correlation data suggest that MB jets play a dominant role in hadron production near midrapidity. Claimed flow phenomena are better explained as jet manifestations agreeing quantitatively with measured jet properties., Comment: 10 pages, 8 figures, Proceedings of XLVII International Symposium on Multiparticle Dynamics, Tlaxcala City, Mexico, September 11-15, 2017

A two-component (soft + hard) model (TCM) of hadron production in high-energy nuclear collisions is applied to ensemble-mean $p_t$ (denoted by $\bar p_t$) data for $p$-$p$, $p$-Pb and Pb-Pb collisions from the relativistic heavy ion collider (RHIC) and large hadron collider (LHC). This $\bar p_t$ TCM is directly related to a recently-published TCM for the charge-multiplicity $n_{ch}$ and collision-energy dependence of $p_t$ spectrum data from $p$-$p$ collisions. Multiplicity dependence of the $p$-$p$ spectrum hard component observed in the previous study is consistent with similar behavior for $\bar p_t$ hard component $\bar p_{th}$. $p$-$p$ $\bar p_t$ $n_{ch}$ dependence is observed to follow a noneikonal trend for the TCM hard component (dijet production $\propto n_{ch}^2$), whereas the trend for Pb-Pb collisions is consistent with the eikonal approximation assumed for the Glauber A-A centrality model. The $p$-Pb trend is intermediate, transitioning from the noneikonal $p$-$p$ trend for more-peripheral collisions to an eikonal trend for more-central collisions. The multiplicity dependence of participant number $N_{part}$ and binary-collision number $N_{bin}$ inferred from $p$-Pb $\bar p_t$ data differs strongly from a Glauber Monte Carlo model of that system. The rapid increase with $n_{ch}$ and large magnitude of $\bar p_t$ for the $p$-$p$ and $p$-Pb systems suggests that minimum-bias jets (TCM hard component) dominate $\bar p_t$ variation. The trend for $\bar p_{th}$ in Pb-Pb collisions is consistent with quantitative modification of jet formation in more-central A-A collisions., Comment: 20 pages, 16 figures

Dijets observed near midrapidity in high-energy nuclear collisions result from large-angle scattering of low-$x$ partons (gluons) within projectile hadrons as a signature manifestation of QCD. Within the same collisions it has been claimed that hydrodynamic flows (radial, elliptic and "higher harmonic" flows) carried by a dense QCD medium or quark-gluon plasma (QGP) dominate the observed hadronic final state. The flow-QGP narrative is imposed {\em a priori} on primary particle data, and of all possible analysis methods a subset A that seems to support that narrative is preferred. The present study explores an alternative minimum-bias (MB) jet narrative -- quantitative correspondence of MB dijet manifestations in the hadronic final state with measured {\em isolated jet} properties. The latter incorporates a different set of methods B that emerge from inductive study of primary particle data without {\em a priori} assumptions. The resulting system of methods and data manifestations is represented by a two-component (soft + hard) model (TCM) of hadron production. A survey of methods reveals that type A tends to discard substantial information carried by primary particle data whereas type B retains almost all information in both primary particle data from nuclear collisions and from isolated jets. The main goal of the present study is a review of MB dijet contributions to high-energy collisions in small and large systems relative to measured isolated-jet properties. Representative analysis methods from types A and B are compared in the context of MB jet manifestations. This study suggests that at least some data features commonly attributed to flows actually result from MB dijets and thereby challenges the flow-QGP narrative., Comment: 25 pages, 28 figures

According to the flow narrative commonly applied to high-energy nuclear collisions a 1D cylindrical-quadrupole component of 2D angular correlations conventionally denoted by quantity $v_2$ is interpreted to represent elliptic flow: azimuth modulation of transverse or radial flow in noncentral nucleus-nucleus (A-A) collisions. The nonjet (NJ) quadrupole component exhibits various properties inconsistent with a flow or hydro interpretation, including the observation that NJ-quadrupole centrality variation in $A$-$A$ collisions has no relation to strongly-varying jet modification ("jet quenching") in those collisions commonly attributed to jet interaction with a dense flowing medium. In the present study I report isolation of quadrupole spectra from $p_t$-differential $v_2(p_t)$ data obtained at the relativistic heavy ion collider (RHIC) and large hadron collider (LHCr). I demonstrate that NJ quadrupole spectra have characteristics very different from the single-particle spectra for most hadrons, that quadrupole spectra indicate a common boosted hadron source for a small minority of hadrons that "carry" the quadrupole structure, that the narrow source-boost distribution is characteristic of an expanding thin cylindrical shell (also strongly contradicting a hydro interpretation), and that in the boost frame a single universal quadrupole spectrum (L\'evy distribution) on transverse mass $m_t$ accurately describes data for several hadron species scaled according to their statistical-model abundances. The quadrupole spectrum shape changes very little from RHIC to LHC energies. Taken in combination those characteristics strongly suggest a unique {\em nonflow} (and nonjet) QCD mechanism for the NJ quadrupole conventionally represented by $v_2$., Comment: 26 pages, 21 figures

According to the flow narrative commonly applied to high-energy nuclear collisions a cylindrical-quadrupole component of 1D azimuth angular correlations is conventionally denoted by quantity $v_2$ and interpreted to represent elliptic flow. Jet angular correlations may also contribute to $v_2$ data as "nonflow" depending on the method used to calculate $v_2$, but 2D graphical methods are available to insure accurate separation. The nonjet (NJ) quadrupole has various properties inconsistent with a flow interpretation, including the observation that NJ quadrupole centrality variation in A-A collisions has no relation to strongly-varying jet modification ("jet quenching") in those collisions commonly attributed to jet interaction with a flowing dense medium. In this presentation I describe isolation of quadrupole spectra from pt-differential $v_2(p_t)$ data from the RHIC and LHC. I demonstrate that quadrupole spectra have characteristics very different from the single-particle spectra for most hadrons, that quadrupole spectra indicate a common boosted hadron source for a small minority of hadrons that "carry" the NJ quadrupole structure, that the narrow source-boost distribution is characteristic of an expanding thin cylindrical shell (strongly contradicting hydro descriptions), and that in the boost frame a single universal quadrupole spectrum (L\'evy distribution) on transverse mass $m_t$ accurately describes data for several hadron species scaled according to their statistical-model abundances. The quadrupole spectrum shape changes very little from RHIC to LHC energies. Taken in combination those characteristics strongly suggest a unique {\em nonflow} (and nonjet) QCD mechanism for the NJ quadrupole conventionally represented by $v_2$., Comment: 6 pages, 6 figures, to appear in proceedings of the XLVI International Symposium on Multiparticle Dynamics

A two-component (soft + hard) model (TCM) of hadron production in yields and spectra derived from the charge-multiplicity dependence of 200 GeV p-p collisions at the relativistic heavy ion collider (RHIC) is extended to describe p-p spectrum data from the large hadron collider (LHC) up to 13 TeV. The LHC data include spectrum ratios that provide only partial information on the TCM. The LHC ratio method is applied to well-understood 200 GeV spectrum data to derive an algebraic link between spectrum ratios and the full TCM. Some aspects of the form of the hard component on transverse momentum are found to be $n_{ch}$ dependent. LHC spectrum ratios are then analyzed to obtain $n_{ch}$ and collision-energy (over three orders of magnitude) dependence of isolated soft and hard TCM spectrum components. The energy dependence of the spectrum soft component is a new result suggesting a relation to Gribov diffusion. The spectrum hard component varies simply and smoothly with $n_{ch}$ suggesting bias of the underlying jet spectrum and linearly with QCD parameter $\log(s/s_0)$, its properties consistent with minimum-bias reconstructed-jet spectrum measurements., Comment: 24 pages, 22 figures

Recent observations of ridge-like structure in $p$-$p$ and $p$-$A$ angular correlations at the RHIC and LHC have been interpreted to imply collective motion in smaller collision systems. It is argued that if correlation structures accepted as manifestations of flow in $A$-$A$ collisions appear in smaller systems collectivity (flow) must extend to the smaller systems. But the argument could be reversed to conclude that such structures appearing in $A$-$A$ collisions may not imply hydrodynamic flow. I present spectrum, correlation and fluctuation data from RHIC $p$-$p$ and Au-Au collisions and $p$-$p$, $p$-Pb and Pb-Pb results from the LHC described accurately by a two-component (soft+dijet) model of hadron production. I also present evidence for a significant $p$-$p$ nonjet (NJ) quadrupole ($v_2$) component with $n_{ch}$ systematics directly related to $A$-$A$ NJ quadrupole systematics. The combination suggests that soft, dijet and NJ quadrupole components are distinct phenomena in all cases, inconsistent with hadron production from a common bulk medium exhibiting collective motion (flow)., Comment: 6 pages, 5 figures, prepared for XLV ISMD 2015

In the context of data modeling and comparisons between different fit models, Bayesian analysis calls that model best which has the largest evidence, the prior-weighted integral over model parameters of the likelihood function. Evidence calculations automatically take into account both the usual chi-squared measure and an Occam factor which quantifies the price for adding extra parameters. Applying Bayesian analysis to projections onto azimuth of 2D angular correlations from 200 GeV AuAu collisions, we consider typical model choices including Fourier series and a Gaussian plus combinations of individual cosine components. We find that models including a Gaussian component are consistently preferred over pure Fourier-series parametrizations, sometimes strongly so. For 0-5% central collisions the Gaussian-plus-dipole model performs better than Fourier Series models or any other combination of Gaussian-plus-multipoles., Comment: 6 pages, 4 figures. Proceedings of the XLV International Symposium on Multiparticle Dynamics, Wildbad Kreuth, 5-9 October 2015

An established phenomenology and theoretical interpretation of $p$-$p$ collision data at lower collision energies should provide a reference for $p$-$p$ and other collision systems at higher energies, against which claims of novel physics may be tested. The description of $p$-$p$ collisions at the relativistic heavy ion collider (RHIC) has remained incomplete even as claims for collectivity and other novelties in data from smaller systems at the large hadron collider (LHC) have emerged recently. In this study we report the charge-multiplicity dependence of two-dimensional (2D) angular correlations and of single-particle (SP) densities on transverse rapidity $y_t$ and pseudorapidity $\eta$ from 200 GeV $p$-$p$ collisions. We define a comprehensive and self-consistent two-component (soft + hard) model (TCM) for hadron production and report a significant $p$-$p$ nonjet (NJ) quadrupole component as a third (angular-correlation) component. Our results have implications for $p$-$p$ centrality, the underlying event (UE), collectivity in small systems and the existence of flows in high-energy nuclear collisions., Comment: 21 pages, 14 figures

Previous measurements of a quadrupole component of azimuth correlations denoted by symbol $v_2$ have been interpreted to represent elliptic flow, a hydrodynamic phenomenon conjectured to play a major role in noncentral nucleus-nucleus collisions. $v_2$ measurements provide the main support for conclusions that a ``perfect liquid'' is formed in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC). However, conventional $v_2$ methods based on one-dimensional (1D) azimuth correlations give inconsistent results and may include a jet contribution. In some cases the data trends appear to be inconsistent with hydrodynamic interpretations. In this study we distinguish several components of 2D angular correlations and isolate a nonjet (NJ) azimuth quadrupole denoted by $v_2\{\text{2D}\}$. We establish systematic variations of the NJ quadrupole on $y_t$, centrality and collision energy. We adopt transverse rapidity $y_t$ as both a velocity measure and as a logarithmic alternative to transverse momentum $p_t$. Based on NJ quadrupole trends we derive a completely factorized universal parametrization of quantity $v_2\{\text{2D}\}(y_t,b,\sqrt{s_{NN}})$ which describes the centrality, $y_t$ and energy dependence. From $y_t$-differential $v_2(y_t)$ data we isolate a quadrupole spectrum and infer a quadrupole source boost having unexpected properties. NJ quadrupole $v_2$ trends obtained with 2D model fits are remarkably simple. The centrality trend appear to be uncorrelated with a sharp transition in jet-related structure that may indicate rapid change of Au-Au medium properties. The lack of correspondence suggests that the NJ quadrupole may be insensitive to such a medium. Several quadrupole trends have interesting implications for hydro interpretations., Comment: 19 pages, 14 figures

Fluctuation measurements of event-wise mean transverse momentum $\langle p_t \rangle$ for p-p and Pb-Pb collisions at the large hadron collider (LHC) have been reported recently. In that study it was concluded that the strength of "nonstatistical" $\langle p_t \rangle$ fluctuations decreases with increasing particle multiplicity $n_{ch}$ (or A-A centrality) and is nearly independent of collision energy over a large interval. Among several potential mechanisms for those trends onset of thermalization and collectivity are mentioned. The LHC analysis employed one fluctuation measure selected from several possibilities. An alternative fluctuation measure reveals strong increase of $p_t$ fluctuations with $n_{ch}$ (or A-A centrality) and collision energy, consistent with previous measurements at the relativistic heavy ion collider (RHIC). The $p_t$ fluctuation data for LHC p-p collisions can be described accurately by a two-component (soft+hard) model (TCM) in which the hard component represents dijet production. The data for Pb-Pb collisions are described accurately by a TCM reference for more-peripheral collisions (suggesting transparent collisions), but the data deviate quantitatively from the reference for more-central collisions suggesting modification of jet formation. Overall fluctuation data trends suggest that minimum-bias jets (minijets) dominate $p_t$ fluctuations at both the LHC and RHIC., Comment: 19 pages, 13 figures

Analysis and interpretation of spectrum and correlation data from high-energy nuclear collisions is currently controversial because two opposing physics narratives derive contradictory implications from the same data---one narrative claiming collision dynamics is dominated by dijet production and projectile-nucleon fragmentation, the other claiming collision dynamics is dominated by a dense, flowing QCD medium. Opposing interpretations seem to be supported by alternative data models, and current model-comparison schemes are unable to distinguish between them. There is clearly need for a convincing new methodology to break the deadlock. In this study we introduce Bayesian Inference (BI) methods applied to angular correlation data as a basis to evaluate competing data models. For simplicity the data considered are projections of 2D angular correlations onto 1D azimuth from three centrality classes of 200 GeV AuAu collisions. We consider several data models typical of current model choices, including Fourier series (FS) and a Gaussian plus various combinations of individual cosine components. We evaluate model performance with BI methods and with power-spectrum (PS) analysis. We find that the FS-only model is rejected in all cases by Bayesian analysis which always prefers a Gaussian. A cylindrical quadrupole cos(2\phi) is required in some cases but rejected for 0-5%-central AuAu collisions. Given a Gaussian centered at the azimuth origin "higher harmonics" cos(m\phi) for m > 2 are rejected. A model consisting of Gaussian + dipole cos(\phi) + quadrupole cos(2\phi) provides good 1D data descriptions in all cases., Comment: 24 pages, 24 figures

The expression "multiple parton interactions" (MPI) denotes a conjectured QCD mechanism representing contributions from secondary (semi)hard parton scattering to the transverse azimuth region (TR) of jet-triggered p-p collisions. MPI is an object of underlying-event (UE) studies that consider variation of TR $n_{ch}$ or $p_t$ yields relative to a trigger condition (leading hadron or jet $p_t$). An alternative approach is 2D trigger-associated (TA) correlations on hadron transverse momentum $p_t$ or rapidity $y_t$ in which all hadrons from all p-p events are included. Based on a two-component (soft+hard) model (TCM) of TA correlations a jet-related TA hard component is isolated. Contributions to the hard component from the triggered dijet and from secondary dijets (MPI) can be distinguished, including their azimuth dependence relative to the trigger direction. Measured $e^+$-$e^-$ and p-\=p fragmentation functions and a minimum-bias jet spectrum from 200 GeV p-\=p collisions are convoluted to predict the 2D hard component of TA correlations as a function of p-p collision multiplicity. The agreement between QCD predictions and TA correlation data is quantitative, confirming a dijet interpretation for the TCM hard component. The TA azimuth dependence is inconsistent with conventional UE assumptions., Comment: 8 pages, 9 figures, proceedings article for XLIV International Symposium on Multiparticle Dynamics, ISMD2014

A method is derived to predict the structure of dijet-related hard components of trigger-associated (TA) hadron correlations from p-p collisions based on measured fragmentation functions (FFs) from e-e or p-pbar collisions and a minimum-bias (MB) jet or scattered-parton spectrum from p-pbar collisions. The method is based on the probability chain rule and Bayes' theorem and relates a trigger-parton--associated-fragment system from reconstructed dijets to a trigger-hadron--associated-hadron system from p-p data. The method is tested in this study by comparisons of FF TA structure with preliminary p-p TA data but can also be applied to p-A, d-A and A-A collisions over a range of energies. Quantitative comparisons of measured TA correlations with FF-derived predictions may confirm a QCD MB dijet mechanism for certain spectrum and correlation structures whose origins are currently questioned and have been attributed by some to collective expansion (flows)., Comment: 22 pages, 17 figures

Measurements of event-ensemble mean transverse momentum $\langle p_t \rangle$ vs charged-hadron multiplicity $n_{ch}$ for $p_t$ spectra from 5 TeV p-Pb and 2.76 TeV Pb-Pb collisions and from p-p collisions for several energies have been reported recently. While in all cases $\langle p_t \rangle$ increases monotonically with $n_{ch}$ the rate of increase is very different from system to system. Comparisons with several theory Monte Carlos reveal substantial disagreements and lead to considerable uncertainty on how to interpret the $\langle p_t \rangle$ data. In the present study we develop a two-component (soft+hard) model (TCM) of $p_t$ production in high energy nuclear collisions and apply it to the $\langle p_t \rangle$ data. The soft component is assumed to be a universal feature of high energy collisions independent of A-B system or energy. The hard-component model is based on the observation that dijet production in p-p collisions does not satisfy the eikonal approximation but does so in A-A collisions. Hard-component properties are determined from previous measurements of hadron spectrum hard components, jet spectra and fragmentation functions. The TCM describes the p-p and Pb-Pb $\langle p_t \rangle$ data accurately, within data uncertainties, and the p-Pb data appear to transition smoothly from p-p to A-A $n_{ch}$ trends., Comment: 11 pages, 8 figures

As the signature manifestation of QCD in high energy nuclear collisions jet production provides essential tests of that theory. But event-wise jet reconstruction can be complex and susceptible to measurement bias. And QCD theory in the form of Monte Carlo models of elementary collisions can also be complex and difficult to test. It may be beneficial to construct a simple static model of jet production in p-p collisions to facilitate data comparisons and model tests. QCD is a logarithmic theory featuring variations with energy scale of the form $\log(s/s_0)$. Jet-related data such as parton fragmentation functions plotted on logarithmic rapidities exhibit self-similar scaling behavior which admits simple and accurate parametrization with only a few parameters. In this study we extend that method to construct a parametrization of jet (scattered parton) momentum spectra based on certain measured logarithmic jet production trends. The parametrization is established with Sp\=pS jet data and then extrapolated for comparison with Tevatron and LHC jet data. In addition, the jet production model from the present study is combined with a parametrization of p-\=p fragmentation functions to predict the minimum-bias jet fragment contribution to hadron $p_t$ spectra. The prediction is compared with published p-p spectrum data to test the self-consistency of the model., Comment: 10 pages, 10 figures

A recent study reports measurements of transverse-energy $E_t$ distributions at mid-rapidity for several high-energy nuclear collision systems. The $E_t$ data are analyzed in the context of constituent-quark (CQ) participants estimated with a Glauber-model simulation. The study concludes that systematic variations of hadron and $E_t$ yields previously interpreted in terms of a two-component soft+hard model (TCM) of hadron production including a dijet (hard) contribution are actually the result of CQ participant trends with only soft production. It is claimed that deviations from linear scaling with the number of nucleon participants of hadron yields vs A-A centrality do not actually arise from dijet production as previously assumed. In the present study we examine the new $E_t$ data in the context of the TCM and compare those results with previous differential spectrum and minimum-bias correlation analysis. We present substantial evidence supporting a significant dijet contribution to all high-energy nuclear collisions consistent with the TCM and conclude that the $E_t$ data, given their systematic uncertainties, fail to support claimed CQ model interpretations., Comment: 24 pages, 14 figures

Some aspects of hadron production in p-p collisions remain unresolved, including the low-hadron-momentum structure of high-parton-energy dijets, separation of triggered dijets from the underlying event (UE), the systematics of multiple parton interactions and possible systematic underestimation of dijet contributions to high-energy nuclear collisions. In this study we apply a minimum-bias trigger-associated (TA) correlation analysis to p-p collisions. We extract a hard component from TA correlations that can be compared with measured jet fragment systematics derived from e-e collisions. The kinematic limits on jet fragment production may be determined. The same method may be extended to A-A collisions where the role of minimum-bias jets in spectra and correlations is strongly contested., Comment: 8 pages, 7 figures, prepared for Proceedings of the XLIIIrd Symposium on Multiparticle Dynamics (ISMD13), Chicago, Sept. 16-20, 2013

A two-component model (TCM) for single-particle $p_t$ spectra describes 200 GeV p-p data accurately. Based on that TCM a spectrum hard component was isolated that is related quantitatively to pQCD predictions for jet fragmentation down to low jet energies ($\approx 3$ GeV). We here address jet-related structure in 2D trigger-associated (TA) correlations as a more-detailed method to explore the kinematic limits of low-energy jet production and low-momentum jet fragment structure in p-p collisions. We derive a TCM for p-p TA correlations that can be used to isolate 2D jet-related structure. Inferred minimum-bias (mainly low-energy) jet-related TA correlations may challenge several major assumptions about jet production in p-p (and A-A) collisions. These results should be relevant to p-p underlying-event studies and Monte Carlo predictions of multiple parton interactions., Comment: 16 pages, 11 figures

The relativistic heavy ion collider (RHIC) was constructed to achieve an asymptotic state of nuclear matter in heavy ion collisions, a near-ideal gas of deconfined quarks and gluons denoted quark-gluon plasma or QGP. RHIC collisions are indeed very different from the hadronic processes observed at the Bevalac and AGS, but high-energy elementary-collision mechanisms are also non-hadronic. The two-component model (TCM) combines measured properties of elementary collisions with the Glauber eikonal model to provide an alternative asymptotic limit for A-A collisions. RHIC data have been interpreted to indicate formation of a {\em strongly-coupled} QGP or "perfect liquid". In this review I consider the experimental evidence that seems to support such conclusions and alternative evidence that may conflict with those conclusions and suggest different interpretations., Comment: 30 pages, 37 figures, invited review for Advances in High Energy Physics

Background: A component of azimuth correlations from high-energy heavy ion collisions varying as $\cos(2\phi)$ and denoted by symbol $v_2$ is conventionally interpreted to represent "elliptic flow," a hydrodynamic manifestation of the initial-state \aa overlap geometry. Several numerical methods are used to estimate $v_2$, resulting in various combinations of "flow" and "nonflow" that reveal systematic biases in the $v_2$ estimates. QCD jets contribute strongly to azimuth correlations and specifically to the $\cos(2\phi)$ component. Purpose: We question the extent of jet-related ("nonflow") bias in and hydrodynamic "flow" interpretations of $v_2$ measurements. Method: We introduce two-dimensional (2D) model fits to angular correlation data that distinguish accurately between jet-related correlation components and a {\em nonjet azimuth quadrupole} that might represent "elliptic flow" if that were relevant. We compare measured jet-related and "flow"-related data systematics and determine the jet-related contribution to $v_2$ measurements. Results: Jet structure does introduce substantial bias to conventional $v_2$ measurements, making interpretation difficult. The nonjet quadrupole exhibits very simple systematics on centrality and collision energy---the two variables factorize. Within a \auau centrality interval where jets show no indication of rescattering or medium effects the nonjet quadrupole amplitude rises to 60% of its maximum value. Conclusions: Disagreements between nonjet quadrupole systematics and hydro theory expectations, the large quadrupole amplitudes observed in more-peripheral \auau collisions and a significant nonzero value in \nn $\approx$ \pp collisions strongly suggest that the nonjet quadrupole does not arise from a hydrodynamic "flow" mechanism., Comment: 16 pages, 9 figures

Certain analysis methods have emerged recently that claim to reveal "higher harmonic flows" in more-central \aa collisions at the RHIC and LHC. But pQCD calculations describe the same structures quantitatively., Comment: 8 pages, 8 figures, Presented at ISMD 2012, Kielce, Poland, 16-21 September 2012

Two aspects of high-energy \pp collisions share common phenomenological elements: (a) A correlation between jet production and \pp centrality is suggested by the transverse partonic structure of hadrons inferred from deep-inelastic scattering data. (b) The {\em underlying event} (UE) is defined as the final-state particles complementary to a triggered high-energy dijet. An observable common to both topics is variation of so-called {\em transverse multiplicity} $N_\perp$ with a $p_{t,trig}$ dijet trigger. We test assumptions associated with \pp collision centrality and the UE. We determine the nature of the UE and explore the relation between jet production and \pp centrality. We use the {\em two-component model} (TCM) of spectra and correlations derived from 200 GeV \pp collisions to construct a simulated particle distribution on $(p_t,n_{ch})$ to predict the $N_\perp$ response to $p_{t,trig}$. The $p_t$ spectrum TCM combined in this analysis with measured minimum-bias \pp angular correlations suggests that the UE includes a substantial contribution from the triggered dijet in addition to the contribution from projectile fragmentation (beam-beam remnants). The jet contribution to $N_\perp$ may represent a universal large-angle base common to all dijets that extends across $2\pi$ azimuth. The analysis further suggests that \pp centrality is not controlled significantly by $p_{t,trig}$ but may be correlated to some extent with an imposed $n_{ch}$ condition, depending on the role of fluctuations. Future correlation studies may better determine the role of \pp centrality. These results may have implications for ongoing RHIC analysis and LHC searches for physics beyond the standard model., Comment: 17 pages, 12 figures