Search

We consider the process e + e − → τ + τ − and calculate the sensitivity of the azimuthal asymmetry in the π − decay channel to F 3 . At √ s = 6 GeV , this asymmetry could lead to a bound of 3 × 10 −3 on F 3 , given 10 7 τ + τ − pairs and transversely polarized initial beams. We also consider partially polarized beams.

It is suggested that the formation of a quark-gluon plasma in relativistic heavy-ion collisions may reveal itself in the azimuthal asymmetry of the ratio of the GF and J Ψ meson yields which can be measured using RICH-type detectors.

We calculate the contribution of vector meson dominance to deeply inelastic lepton-nucleon scattering in the kinematic region of the HERMES experiment. The results obtained show that this contribution is quite significant. Together with the fact that there exist very striking left-right asymmetries for hadrons produced in single-spin hadron-hadron collisions, these results imply that the single-spin azimuthal asymmetry observed by HERMES cannot be simply regarded as a pure fragmentation effect.

Dihadron fragmentation functions describe the probability that a quark fragments into two hadrons plus other undetected hadrons. In particular, the so-called interference fragmentation functions describe the azimuthal asymmetry of the dihadron distribution when the quark is transversely polarized. They can be used as tools to probe the quark transversity distribution in the nucleon. Recent studies on unpolarized and polarized dihadron fragmentation functions are presented, and we discuss their role in giving insights into transverse spin distributions., To appear in the proceedings of the 19th International Spin Physics Symposium, Sept 27 - Oct 2, 2010, Juelich, Germany. To be published in JPCS

One-baseline 1-h Very Long Baseline Interferometry (VLBI) Intensive sessions are carried out every day to determine Universal Time (UT1). Azimuthal asymmetry of tropospheric delays around the stations is usually ignored and not estimated because of the small number of observations. In this study we use external information about the asymmetry for the Intensive sessions between Tsukuba (Japan) and Wettzell (Germany), which are carried out on Saturdays and Sundays (1) from direct ray-tracing for each observation at Tsukuba and (2) in the form of linear horizontal north and east gradients every 6 h at both stations. The change of the UT1 estimates is at the 10 μs level with maximum differences of up to 50 μs, which is clearly above the formal uncertainties of the UT1 estimates (between 5 and 20 μs). Spectral analysis reveals that delays from direct ray-tracing for the station Tsukuba add significant power at short periods (1–2 weeks) w.r.t. the state-of-the-art approach, and comparisons with length-of-day (LOD) estimates from Global Positioning System (GPS) indicate that these ray-traced delays slightly improve the UT1 estimates from Intensive sessions.

The azimuthal asymmetry of the polarized backscattering cone and the intimately related polarization opposition effect (POE) are corollaries of the theory of coherent backscattering (CB) valid in the asymptotic limit of very small particle packing density. In this paper we use numerically exact solutions of the Maxwell equations to study the evolution of these and other manifestations of CB as the packing density in a multiparticle group increases from zero to values typical of actual particle suspensions and particulate surfaces. Our results reveal a remarkable robustness of virtually all effects predicted by the low-density concept of CB and allow us to conclude that the azimuthal asymmetry and POE observed in the laboratory for densely packed discrete random media are indeed caused by CB.

In this chapter, which is intended to serve as a quick reference, we define terms, quantities and relations that are frequently used in air shower terminology. Italic terms in the explanations of Sect. 21.2 below indicate that they themselves are defined in this section. The topics are listed in alphabetic order. Details of the topics listed here can be found with the help of the Subject Index in the appropriate Chapters.

The disconnection of an underwater bubble illustrates how slight initial asymmetries can prevent the formation of a finite-time singularity. Creating a singularity by focusing a finite amount of energy dynamically into a vanishingly small amount of material requires that the initial condition be perfectly symmetric. In reality, imperfections are always present. We show a slight azimuthal asymmetry in the initial shape of the bubble neck excites vibrations that persist over time. As a result, the focusing singularity is generically preempted by a smooth contact.

We discuss how the chemical composition of QCD jets is altered by final state interactions in surrounding nuclear matter. We describe this process through conversions of leading jet particles. We find that conversions lead to an enhancement of kaons at high transverse momentum in Au+Au collisions at RHIC, while their azimuthal asymmetry v_2 is suppressed., Comment: Contribution to the 4th international workshop High-pT physics at LHC 09, Prague; 6 pages, 6 figures

Semi-inclusive {pi}{sup +} electroproduction on protons has been measured with the CLAS detector at Jefferson Lab. The measurement was performed on a liquid-hydrogen target using a 5.75 GeV electron beam. The complete five-fold differential cross sections were measured over a wide kinematic range including the complete range of azimuthal angles between hadronic and leptonic planes, {phi}, enabling us to separate the {phi}-dependent terms. Our measurements of the {phi}-independent term of the cross section at low Bjorken x were found to be in fairly good agreement with pQCD calculations. Indeed, the conventional current fragmentation calculation can account for almost all of the observed cross section, even at small {pi}{sup +} momentum. The measured center-of-momentum spectra are in qualitative agreement with high-energy data, which suggests a surprising numerical similarity between the spectator diquark fragmentation in the present reaction and the antiquark fragmentation measured in e{sup +}e{sup -} collisions. We have observed that the two {phi}-dependent terms of the cross section are small. Within our precision the cos2{phi} term is compatible with zero, except for the low-z region, and the measured cos{phi} term is much smaller in magnitude than the sum of the Cahn and Berger effects.

International audience; Taking advantage of emerging technology in mirror manufacturing and spacecraft formation flying, Simbol-X will push grazing incidence imaging up to ~80 keV, providing an improvement of roughly three orders of magnitude in sensitivity and angular resolution compared to all instruments that have operated so far above 10 keV. This will open a new window in X-ray astronomy, allowing breakthrough studies on black hole physics and census and particle acceleration mechanisms. We discuss here synergies between Simbol-X and the main multiwavelength facilities that will operate in the next decade, and present a quantitative comparison between Simbol-X and its main competitors, NuStar and Astro-H.

Extensive IUE observations from 1987–96 have provided compelling evidence for azimuthal asymmetry in the winds of Be stars. Two identified types of wind/FUV flux behavior are briefly discussed. Interpretations based upon both nonradial pulsations and rotation of one or more active regions appear plausible.

We analyze measures of the azimuthal asymmetry, in particular the participant harmonic moments, e∗, in a variety of Glauber-like models for the early stage of collisions at RHIC. Quantitative comparisons indicate substantial model dependence for e∗, reflecting different effective number of sources, while the dependence of the scaled standard deviation σ(e∗)/e∗ on the particular Glauber model is weak. For all the considered models the values of σ(e∗)/e∗ range from ∼ 0.5 for the central collisions to ∼ 0.3-0.4 for peripheral collisions. These values, dominated by statistics, change only by 10-15% from model to model. For central collisions and in the absence of correlations between the location of sources we obtain through the use of the central limit theorem the simple analytic formula σ(e∗)/e∗(b = 0) ≃ √

The azimuthal elliptic asymmetry v2 observed in heavy ion collisions, is usually associated with properties of the medium created in the final state. We compute the azimuthal asymmetry which is due to multiple interactions of partons at the initial stage of nuclear collisions, and which is also present in $pA$ collisions. In our approach the main source of azimuthal asymmetry is the combination of parton multiple interactions with the steep variation of the nuclear density at the edge of nuclei. We apply the light-cone dipole formalism to compute the azimuthal asymmetry of prompt photons yield from parton-nucleus, proton-nucleus and nucleus-nucleus collisions at the RHIC energy., 13 pages, 4 figures, Eq.(4) corrected, figures and references updated. The version to appear in Nucl. Phys. A

The azimuthal asymmetry of direct photons originating from primary hard scatterings between partons is calculated. This can be accounted for by the inclusion of the color dipole orientation, which is sensitive to the rapid variation of the nuclear profile. To this end we introduce the dipole orientation within the saturation model of Golec-Biernat and W\"usthoff, while preserving all its features at the cross-section level. We show that the direct photon elliptic anisotropy v2 coming from this mechanism changes sign and becomes negative for peripheral collisions, albeit it is quite small for nuclear collisions at the RHIC energy., Comment: 6 pages, 6 figures, Based on talk given by A.H.R. at II LAWHEP, Sao Miguel das Missoes, Brazil, December 3-7, 2007

A review of the collisional, collective, and resonance phenomena in planetary rings is presented. The following questions are examined: the reasons for the existence of planetary rings and the properties of a typical particle, the collisional breaking of loose bodies, and the azimuthal asymmetry effect for the rings of Saturn. A transfer theory is being developed for differentially rotating disks of inelastic particles, and the collective instabilities of planetary rings and a protoplanetary disk are discussed. A model for the resonance origin for the rings of Uranus is described, which enabled one to predict unknown satellites of Uranus that were later discovered by Voyager-2. The problem of the stability of the rings of Uranus is examined.

Experimental results are presented on proton and pion interactions at 300 GeV with silver and bromine nuclei in emulsions yielding high multiplicities N h ⩾ 28 of heavy fragments that may be considered due to total disintegration of nuclei. The following characteristics were found: multiplicities of emitted particles, angular distributions of characteristics groups of particles, and the probability value of azimuthal asymmetry of b -particles.

We present a systematic study of elliptic flow as a function of centrality, pseudorapidity, transverse momentum and energy for Cu+Cu and Au+Au collisions from the PHOBOS experiment. New data on elliptic flow in Cu+Cu collisions at 22.4 GeV are shown. Elliptic flow scaled by participant eccentricity is found to be similar for both systems when collisions with the same number of participants or the same average area density are compared. This similarity is observed over a wide range in pseudorapidity and transverse momentum, indicating that participant eccentricity is the relevant quantity for generating the azimuthal asymmetry leading to the observed elliptic flow., 5 pages, 4 figures, the 19th International Conference On Ultra relativistic Nucleus-Nucleus Collisions (Quark Matter 2006), Shanghai China, Nov. 14-20, 2006

The nuclear‐mass dependence of the beam‐spin asymmetry (BSA) in deeply virtual Compton scattering has been measured at HERMES. The BSA ratios of Nuclei to Hydrogen or Deuterium BSAs have been extracted in coherent and incoherent‐enriched kinematic regions separately.

The ground-based measurements of the Global Positioning System (GPS) allow estimation of the tropospheric delay along the slanted signal paths through the atmosphere. The meteorological exploitation of such slant delay (SD) observations relies on the hypothesis of azimuthal asymmetry of the information content. This article addresses the validity of the hypothesis. A new concept of asymmetricity is introduced for studying the SD observations and their model counterparts. The asymmetricity is defined as the ratio of the absolute asymmetric delay component to total SD. The model counterparts are determined from 3-h forecasts of a numerical weather prediction (NWP) model, run with four different horizontal resolutions. The SD observations are compared with their model counterparts with emphasis on cases of high asymmetricity in order to see whether the observed asymmetry is a real atmospheric signature. The asymmetricity is found to be of the order of a few parts per thousand. Thus, the asymmetric delay component barely exceeds the assumed standard deviation of the SD observation error. However, the observed asymmetric delay components show a statistically significant meteorological signal. Benefit of the asymmetric SD observations is therefore expected to be taken in future, when NWP systems will explicitly represent the small-scale atmospheric features revealed by the SD observations.

CASTOR is a novel tungsten/quartz EM and HAD calorimeter, specially designed for the study of “long-penetrating hadrons”, observed in hadron-rich Cosmic-Ray events and suggested to be Strangelets. Strangelets are proposed to be formed in the baryon-rich, very forward fragmentation region, through the creation of deconfined quark matter in ultra-relativistic A + A collisions at the LHC. Such objects, if they exist, should be detected and identified in the 10.3 λ I calorimeter by their azimuthal asymmetry in energy deposition and their large magnitude of fluctuations in the transition curves, as compared to normal events. We briefly present the calorimeter and discuss the MC simulations for the identification of Strangelets.

A short summary of results of recent simulations of (un)polarized Drell-Yan experiments is presented here. Dilepton production in $pp$, $\bar{p}p$, $\pi^-p$ and $\pi^+p$ scattering is considered, for several kinematics corresponding to interesting regions for experiments at GSI, CERN-Compass and RHIC. A table of integrated cross sections, and a set of estimated error bars on measurements of azimuthal asymmetries (associated with collection of 5, 20 or 80 Kevents) are reported., Comment: 8 pages, 7 figures in .eps format; to appear in the Proceedings of the International Workshop on Transverse Polarisation Phenomena in Hard Processes (Transversity 2005), Villa Olmo (Como), 7-10th September 2005; World Scientific style files included

Energy and angular distributions of the tau decay products in the CERN-to-Gran Sasso $\nu_\tau$ appearance experiments are studied for the decay modes $\tau\to\pi\nu$ and $\tau\to l\bar\nu\nu$ (l=e or mu). We find that the decay particle distributions in the laboratory frame are significantly affected by the tau polarization. Rather strong azimuthal asymmetry of $pi^-$ and $l^-$ about the tau momentum axis is predicted, which may have observable consequences even at small statistics experiments., Comment: 14 pages, 6 eps figures; comments on Fig. 1 added, Fig. 4 improved to see clearly

We study the azimuthal asymmetry of the unpolarized Drell-Yan in the framework of the T-odd functions. We find, on the basis of quite general arguments, that for |{\bf q}_{\perp}| << Q such an asymmetry decreases as Q^{-2}, where {\bf q}_{\perp} and Q are respectively the transverse momentum and the center-of-mass energy of the muon pair. The experimental results support this conclusion., 15 pages, 4 figures. Presented at "HiX2004", Marseille, July 26-28, 2004

A new sensing configuration is proposed for simultaneous measurement of strain and temperature that relies on a single long period grating written by the electric arc technique. The underlying principle is the azimuthal asymmetry induced by the electric arc fabrication technique, which results in a device with polarization dependent insertion loss sensitive to both temperature and strain. With the proposed configuration, resolutions of ±2.8°C/√Hz and ±13.9μe/√Hz are obtained for temperature and strain measurements, respectively.

Measurements of the production of forward high-energy pi(0) mesons from transversely polarized proton collisions at root200 GeV are reported. The cross section is generally consistent with next-to-leading order perturbative QCD calculations. The analyzing power is small at x(F) below about 0.3, and becomes positive and large at higher x(F), similar to the trend in data at roots less than or equal to20 GeV. The analyzing power is in qualitative agreement with perturbative QCD model expectations. This is the first significant spin result seen for particles produced with p(T)>1 GeV/c at a polarized proton collider.

We consider a rescattering mechanism to calculate a leading twist $T$-odd pion fragmentation function, a candidate for filtering the transversity properties of the nucleon. We evaluate the single spin azimuthal asymmetry for a transversely polarized target in semi-inclusive deep inelastic scattering (for HERMES kinematics) and the double $T$-odd $\cos2\phi$ asymmetry in this framework., Comment: To appear in the proceedings of 8th Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2003), New York, New York, 19-24 May 2003

We consider the cos(phi) dependence of the longitudinal double-spin asymmetry for charged pion electroproduction in semi-inclusive deep inelastic scattering, emphasizing intrinsic transverse momentum effects. This azimuthal asymmetry allows to measure the cos(phi) moments of the unpolarized and double-spin cross-section, simultaneously. The size of the asymmetry, in the approximation where all twist-3 interaction-dependent distribution and fragmentation functions are set to zero, is estimated for HERMES kinematics; both the spin-independent and the double-spin cos(phi) moments are predicted to be sizeable and negative., LaTeX, 4 pages, 4 figures. Discussion on the acceptance effects added; recent parameterizations of distribution and fragmentation functions used, figures replaced. Final version to appear in Physics Letters B

We discuss a simple generic model of ``jet quenching'' in which matter absorption is defined by one parameter. We show that as absorption grows, the azimuthal asymmetry parameter ${v}_{2}$ grows as well, reaching the finite limit ${v}_{2}^{*}$ which has a simple geometric interpretation. We show that this limit is still below the experimental values for $6g{p}_{t}g2 \mathrm{GeV},$ according to preliminary data from the STAR experiment at RHIC. We thus conclude that jet quenching models alone cannot account for the observed phenomenon, and speculate about alternative scenarios.

The linearly polarized \ensuremath{\gamma}-ray beam produced by the $\mathrm{HI}\ensuremath{\gamma}\mathrm{S}$ facility has been used to determine the parity of two previously known dipole excitations in ${}^{88}\mathrm{Sr}.$ The azimuthal asymmetry of \ensuremath{\gamma} rays produced in the process of nuclear resonance fluorescence indicated that the dipole state at 4.742 MeV, recently discussed as a new form of $M1$ excitation, is in fact a ${1}^{\ensuremath{-}}$ $(E1)$ state. The ${1}^{\ensuremath{-}}$ state at 4.742 MeV must, therefore, be reconsidered as the ${J}^{\ensuremath{\pi}}{=1}^{\ensuremath{-}}$ member of the quadrupole-octupole coupled two-phonon multiplet. A second state at 7.535 MeV was also assigned ${J}^{\ensuremath{\pi}}{=1}^{\ensuremath{-}}.$

The azimuthal asymmetry of $J/\psi$ suppression in non-central heavy-ion collisions is studied within a dynamic model of $J/\psi$ suppression in a deconfined partonic medium. Within this model, $J/\psi$ suppression in heavy-ion collisions is caused mainly by the initial state nuclear absorption and dissociation via gluon-$J/\psi$ scattering in deconfined partonic medium. Only the second mechanism gives arise to azimuthal asymmetry of the final $J/\psi$ production. We demonstrate that if there is an onset of suppression by quark-gluon plasma (QGP) in the NA50 data, it must be accompanied by the non-vanishing azimuthal asymmetry. Using the same critical density above which the QGP effect enters, we predict the azimuthal asymmetric coefficient $v_2$ as well as the survival probability for $J/\psi$ at the RHIC energy., Comment: 10 pages, 2 EPS figures, final version in Phys. Lett. B

The azimuthal pattern of transverse energy flow in nuclear collisions at RHIC and LHC energies is considered. We show that the probability distribution of the event-by-event azimuthal disbalance in transverse energy flow is essentially sensitive to the presence of the semihard minijet component., Comment: 6 pages, 2 figures

An overview is given of recent results on hard exclusive production of vector and pseudoscalar mesons, obtained by the HERMES experiment. Cross sections for ρ0-production by longitudinal photons are presented. For pion-production the azimuthal asymmetry for a longitudinally polarized proton target and −t-distribution are discussed.

We discuss the quark transversity distribution function and a possible way to access it through the measurement of single spin azimuthal asymmetry in semi-inclusive single pion electroproduction on a transversely polarized target., 5 pages, Latex using aipproc.sty (included), to appear in proceedings of "Second Workshop on Physics with an Electron Polarized Light Ion Collider", Sept. 14-16, 2000, MIT, Cambridge, USA

We propose a new method of the determination of $R^{D}=\sigma_{L}^{D}/\sigma_{T}^{D}$ from the dependence of the diffractive cross section on the azimuthal angle between the electron scattering and proton scattering planes. The method is based on our finding of the model independence of the ratio of the $LT$ interference and transverse diffractive structure functions. The predicted azimuthal asymmetry is substantial and can be measured at HERA. We show that the accuracy of our reconstruction of $R^{D}$ is adequate for a reliable test of an important pQCD prediction of $R^{D}\gsim 1$ for large $\beta$.

We discuss the dependence of elliptic flow on transverse momentum and number of participating nucleons in the framework of a multi-source model, and argue that the geometry of an initial overlap region of interaction determines the measured azimuthal asymmetry. With the help of v2(PT) fitting, the participant nucleon number at a fixed impact parameter is calculated by a geometrical picture of the participant–spectator model. In the combined framework of the two models, our results are approximately in agreement with the experimental data.

The prospect of observing parity violation from the strong interaction in relativistic heavy?ion collisions has recently gained great attention. We present the measurements of the azimuthal asymmetry of charged hadron production in Pb?Pb collisions at = 2.76 TeV via the study of a parity even 3- and 2-particle azimuthal correlator. The results for LHC energies are compared to the ones reported by RHIC experiments but also to different models and to predictions from theory. The possible implications of these measurements to the local parity violation and the contribution from background effects are discussed.

Azimuthal distributions of fragments with respect to the reaction plane are studied in the Ar+V system as a function of beam energy. Light charged particles are found to exhibit an enhanced emission in the reaction plane which increases with the mass of the detected particle. As the beam energy is increased, the asymmetry decreases. Possible mechanisms behind the asymmetry, such as rotational collective motion and directed transverse momentum, are discussed.

Studies of radiation of electrons, moving near crystalline planes (diamond and germanium single crystals), which we have carried out at an electron energy of 4.3 GeV have shown a considerable azimuthal asymmetry of gamma-quanta angular distributions in the range of ϵ = 0.3−4.0 GeV. In our opinion this effect is connected with the polarization of the mentioned radiation.

1. The cassettes of the VVER show considerable nonuniformity in burnup over the height and cross section; this to decrease as the general burnup increases. 2. Absorbing elements reduce the nonuniformity in the height distribution somewhat, but increase the nonuniformity over the cross section of the cassette and substantially reduce the extent of burnup in adjacent fuel pins. 3. Boron control produces substantially less nonuniformity in burnup both in height and cross section. 4. There is considerable nonuniformity in burnup across the cross section of a fuel pin on account of self-screening; there is also appreciable azimuthal asymmetry in burnup in a pin, which is particularly prominent for239Pu, as is clear from the distribution of106Ru.

Data on azimuthal correlations and their rapidity dependence are presented in inclusive and semi-inclusive reactions π − p → π + π + X,→ π − π − X and π + π − X at 40 GeV/ c . They show a long range as well as a short range effect. The short range effect, leading to different behaviour of d N /d φ near φ = 0 of like and unlike pion pairs is explained by identical and unidentical particle statistics. The predictions of the independent cluster model for the azimuthal asymmetry are in qualitative agreement with data of this experiment as well as those at 102 and 205 GeV/ c .

Mutually consistent measurements of elastic proton scattering and resonance absorption show that the width of the 9.17 MeV level in $^{14}\mathrm{N}$ ($\ensuremath{\Gamma}=135\ifmmode\pm\else\textpm\fi{}8$ eV) is almost twice as large as the accepted literature value. The positive parity is unambiguously confirmed. The excitation energy is determined to be 9172.5\ifmmode\pm\else\textpm\fi{}0.3 keV, based upon a cascade-crossover technique with a $^{56}\mathrm{Co}$ source for calibration. The expected azimuthal asymmetry of the resonance fluorescence of the plane-polarized photons at this resonance is demonstrated quantitatively.