Search

Ultra-High-Energy Cosmic Rays (UHECRs), particles characterized by energies exceeding $10^{18}$ eV, are generally believed to be accelerated electromagnetically in high-energy astrophysical sources. One promising mechanism of UHECR acceleration is magnetized turbulence. We demonstrate from first principles, using fully kinetic particle-in-cell simulations, that magnetically dominated turbulence accelerates particles on a short timescale, producing a power-law energy distribution with a rigidity-dependent, sharply defined cutoff well approximated by the form $f_{\rm cut}\left({E, E_{\rm cut}}\right) = {\text{sech}}\left[ ( {{E}/{E_{\rm cut}}} )^2 \right]$. Particle escape from the turbulent accelerating region is energy-dependent, with $t_{\rm esc} \propto E^{-\delta}$ and $\delta \sim 1/3$. The resulting particle flux from the accelerator follows $dN/dEdt \propto E^{-s} {\text{sech}}\left[ ( {{E}/{E_{\rm cut}}} )^2 \right]$, with $s \sim 2.1$. We fit the Pierre Auger Observatory's spectrum and composition measurements, taking into account particle interactions between acceleration and detection, and show that the turbulence-associated energy cutoff is well supported by the data, with the best-fitting spectral index being $s = 2.1^{+0.06}_{-0.13}$. Our first-principles results indicate that particle acceleration by magnetically dominated turbulence may constitute the physical mechanism responsible for UHECR acceleration.

We calculate the arrival direction distribution of ultra-high-energy cosmic rays (UHECRs) with a new suite of models of the Galactic magnetic field (GMF), assuming sources follow the large-scale structure of the Universe. Compared to previous GMF models, the amplitude of the dipole component of the UHECR arrival flux is significantly reduced. We find that the reduction is due to the accidentally coinciding position of the peak of the extragalactic UHECR flux and the boundary of strong flux demagnification due to the GMF toward the central region of the Galaxy. This serendipitous sensitivity of UHECR anisotropies to the GMF model will be a powerful probe of the source distribution as well as Galactic and extragalactic magnetic fields. Demagnification by the GMF also impacts visibility of some popular source candidates.

We propose that ultrahigh energy cosmic rays are produced in binary neutron star mergers. Interpreting the highest energy events as r-process nuclei eliminates the need for exotic sources, while the observed near-universal maximum rigidity of ultrahigh energy sources can be understood as due to the uniformity of jets generated by the gravitationally-driven dynamo, given the narrow range of total binary neutron star masses. We discuss evidence for this scenario, and its prediction of coincidences between neutrinos above 10 PeV and gravitational waves.

The Telescope Array Collaboration recently reported the detection of a cosmic-ray particle, "Amaterasu", with an extremely high energy of $2.4\times10^{20}$ eV. Here we investigate its probable charge and the locus of its production. Interpreted as a primary iron nucleus or slightly stripped fragment, the event fits well within the existing paradigm for UHECR composition and spectrum. Using the most up-to-date modeling of the Galactic magnetic field strength and structure, and taking into account uncertainties, we identify the likely volume from which it originated. We estimate a localization uncertainty on the source direction of 6.6\% of $4\pi$ or 2726 deg$^2$. The uncertainty of magnetic deflections and the experimental energy uncertainties contribute about equally to the localization uncertainty. The maximum source distance is 8-50 Mpc, with the range reflecting the uncertainty on the energy assignment. We provide sky maps showing the localization region of the event and superimpose the location of galaxies of different types. There are no candidate sources among powerful radio galaxies. An origin in AGNs or star-forming galaxies is unlikely but cannot be completely ruled out without a more precise energy determination. The most straightforward option is that Amaterasu was created in a transient event in an otherwise undistinguished galaxy., Comment: 9 pages, 5 figures

A dipole anisotropy in ultra-high-energy cosmic ray (UHECR) arrival directions, of extragalactic origin, is now firmly established at energies E > 8 EeV. Furthermore, the UHECR angular power spectrum shows no power at smaller angular scales than the dipole, apart from hints of possible individual hot or warm spots for energy thresholds $\gtrsim$40 EeV. Here, we exploit the magnitude of the dipole and the limits on smaller-scale anisotropies to place constraints on two quantities: the extragalactic magnetic field (EGMF) and the number density of UHECR sources or the volumetric event rate if UHECR sources are transient. We also vary the bias between the extragalactic matter and the UHECR source densities, reflecting whether UHECR sources are preferentially found in over- or under-dense regions, and find that little or no bias is favored. We follow Ding et al. (2021) in using the Cosmic Flows 2 density distribution of the local universe as our baseline distribution of UHECR sources, but we improve and extend that work by employing an accurate and self-consistent treatment of interactions and energy losses during propagation. Deflections in the Galactic magnetic field are treated using both the full JF12 magnetic field model, with random as well as coherent components, or just the coherent part, to bracket the impact of the GMF on the dipole anisotropy. This Large Scale Structure (LSS) model gives good agreement with both the direction and magnitude of the measured dipole anisotropy and forms the basis for simulations of discrete sources and the inclusion of EGMF effects.

We present a suite of models of the coherent magnetic field of the Galaxy (GMF) based on new divergence-free parametric functions describing the global structure of the field. The model parameters are fit to the latest full-sky Faraday rotation measures of extragalactic sources (RMs) and polarized synchrotron intensity (PI) maps from WMAP and Planck. We employ multiple models for the density of thermal and cosmic-ray electrons in the Galaxy, needed to predict the skymaps of RMs and PI for a given GMF model. The robustness of the inferred properties of the GMF is gauged by studying many combinations of parametric field models and electron density models. We determine the pitch angle of the local magnetic field (11+/-1 deg.), explore the evidence for a grand-design spiral coherent magnetic field (inconclusive), determine the strength of the toroidal and poloidal magnetic halo fields below and above the disk (magnitudes the same for both hemispheres within 10%), set constraints on the half-height of the cosmic-ray diffusion volume (>2.9 kpc), investigate the compatibility of RM- and PI-derived magnetic field strengths (compatible under certain assumptions) and check if the toroidal halo field could be created by the shear of the poloidal halo field due to the differential rotation of the Galaxy (possibly). A set of eight models is identified to help quantify the present uncertainties in the coherent GMF -- spanning different functional forms, data products and auxiliary input, and maximizing the differences in their predictions. We present the corresponding skymaps of rates for axion-photon conversion in the Galaxy, and deflections of ultra-high energy cosmic rays., Comment: 40 pages, 27 figures, code available at https://doi.org/10.5281/zenodo.10627090

We compare precision $e^+e^-$ to $\mu^+\mu^-$ cross section measurements by BESIII in the E_cm =3.8-4.6 GeV range, to predictions based on measured R_had data. The consistency is poor (p-value <0.012). Allowing for resonance contributions not seen in R_had gives an excellent fit, with the state at 4421 MeV ( 4.6 sigma) giving insight into the psi(4415) and the 3.1 sigma structure at 4211 MeV, if confirmed, being a new, very narrow resonance. This analysis shows the power of precision $e^+e^-$ to $\mu^+\mu^-$ measurements to uncover or probe otherwise difficult to access states.

We derive and explicitly display the internal wave function of a color-, flavor- and spin- singlet dibaryon composed of uuddss quarks in a spatially symmetric state, in the approximation of exact SU(3) flavor symmetry. This wavefunction shows that the often-used superposition of Lambda Lambda, N Xi and Sigma Sigma baryons, relevant for di-baryon molecules, accounts for only 1/5 of a spatially symmetric six-quark color-flavor-spin-singlet state, with the remaining 4/5 consisting of products of color-octet baryons. Using the correct wavefunction has important implications for calculations of the mass of the lowest-lying flavor-singlet dibaryon, as we illustrate using the Cornell potential. We also provide a compact representation of the state in terms of creation operators, and comment on the impact of not using the optimal operator in lattice studies of this system., Comment: v2: Added citations to related earlier work brought to our attention after posting of v1: Ref. [12] and R. L. Jaffe, private communication (in footnote 2)

A color-flavor-spin singlet state of six quarks $uuddss$ ($S$, or sexaquark) has been argued to be a potentially undiscovered deeply bound, long-lived hadron. Theoretical calculations of the $S$ mass have been made in the literature, widely varying from deeply-bound $\sim 1.2$ GeV to weakly-bound $\sim2.2$ GeV. Given the spread of the mass predictions, it is vital to derive observational constraints on the state as a function of the mass. The transition rates between $S$ and two baryons are governed by $\tilde{g}$, the effective Yukawa coupling between $S$ and two baryons with the same quantum numbers as $S$. In this paper, we place strong observational constraints on $\tilde{g}$, improving on various previous limits; additional limits assuming $S$ is dark matter are also presented., Comment: 18 pages, 8 figures. v2 added a literature review section and improved presentation clarity

We simulate the evolution of the helicity of relic neutrinos as they propagate to Earth through a realistic model of the Galactic magnetic field, improving upon the rough estimates in the literature. For magnetic moments consistent with experimental bounds and several orders of magnitude smaller, we confirm that the helicity of relic neutrinos and anti-neutrinos rotates so much that the spin projection changes by $\mathcal{O}$(1). However, as we show, the total event rate in an inverse tritium beta decay (ITBD) experiment changes by less than a few percent, unless the lightest neutrino has mass of order 0.001 eV or less. Such a tiny reduction in the absolute rate relative to the standard model value would be very difficult to establish, even if detecting relic neutrinos were routine. However as we show, the \emph{directional anisotropy} of the rate in a \emph{polarized} ITBD detector is $\gtrsim \mathcal{O}$(10\%) as long as the lightest neutrino mass is $\gtrsim \mathcal{O}$(0.01 eV). Thus with percent-level error bars on the absolute neutrino flux and its directional anisotropy, both the mass and magnetic moment of the relic neutrinos can in principle be probed if they are within a few orders of magnitude of current bounds., Comment: 11 pages,10 figures

The 2021-22 High-Energy Physics Community Planning Exercise (a.k.a. ``Snowmass 2021'') was organized by the Division of Particles and Fields of the American Physical Society. Snowmass 2021 was a scientific study that provided an opportunity for the entire U.S. particle physics community, along with its international partners, to identify the most important scientific questions in High Energy Physics for the following decade, with an eye to the decade after that, and the experiments, facilities, infrastructure, and R&D needed to pursue them. This Snowmass summary report synthesizes the lessons learned and the main conclusions of the Community Planning Exercise as a whole and presents a community-informed synopsis of U.S. particle physics at the beginning of 2023. This document, along with the Snowmass reports from the various subfields, will provide input to the 2023 Particle Physics Project Prioritization Panel (P5) subpanel of the U.S. High-Energy Physics Advisory Panel (HEPAP), and will help to guide and inform the activity of the U.S. particle physics community during the next decade and beyond., Comment: 75 pages, 3 figures, 2 tables. This is the first chapter and summary of the full report of the Snowmass 2021 Workshop. This version fixes an important omission from Table 2, adds two references that were not available at the time of the original version, fixes a minor few typos, and adds a small amount of material to section 1.1.3

Cosmic Probes of Fundamental Physics take two primary forms: Very high energy particles (cosmic rays, neutrinos, and gamma rays) and gravitational waves. Already today, these probes give access to fundamental physics not available by any other means, helping elucidate the underlying theory that completes the Standard Model. The last decade has witnessed a revolution of exciting discoveries such as the detection of high-energy neutrinos and gravitational waves. The scope for major developments in the next decades is dramatic, as we detail in this report., Comment: Report of theTopical Group on Cosmic Probes of Fundamental Physics, for the U.S. decadal Particle Physics Planning Exercise (Snowmass 2021)

Interactions of ultrahigh energy cosmic rays in the surroundings of their accelerators can naturally explain the observed spectrum and composition of UHECRs, including the abundance of protons below the ankle. We show that astrophysical properties of the UHECR source environment such as the temperature, size, and magnetic field can be constrained by UHECR and neutrino data. Applying this to candidate sources with a simple structure shows that starburst galaxies are consistent with these constraints, but galaxy clusters may be in tension with them. For multi-component systems like AGNs and GRBs the results are indicative but customized analysis is needed for definitive conclusions.

The experimental value of g-2 of the muon is larger by $4.2 \sigma$ than the Standard Model prediction based on the hadronic vacuum polarization contribution (HVP) determined from the measured R-ratio, $\sigma(e^+e^- \! \rightarrow \! \mathit{hadrons})/\sigma(e^+e^- \! \rightarrow \!\mu^+ \mu^-)$; the HVP calculated in lattice QCD also significantly exceeds the measured R-ratio value. We show here that these discrepancies can be explained by an undetected contribution to $e^+e^- \! \rightarrow \! \mathit{hadrons}$ as could arise from production of neutral, long-lived hadrons which have not previously been identified. We suggest two candidates for the new hadrons and propose several experimental tests., Comment: v2 elaborates some points, adds some references and generally improves the presentation

The neutral, flavor singlet scalar uuddss bound state -- the sexaquark, S -- may have a low enough mass to be stable or extremely long-lived. Here we review mass estimates and production expectations and show that laboratory experiments to date do not rule out such a long-lived state. An S with mass below 2054 MeV is either absolutely stable or has a lifetime greater than the age of the Universe. Detection of a stable S in accelerator experiments is very challenging. An examination of the experimental literature shows that such an effectively stable state would have escaped detection. The strongest laboratory constraint on a long-lived S comes from the lower-bound on its formation time in a doubly-strange hypernucleus; this constraint is, however, not stringent enough to exclude a stable S. We develop strategies to discover it. A stable S would be an attractive dark matter candidate. Relevant astrophysical and cosmological observations, which show that sexaquark dark matter is consistent with all current knowledge, are briefly reviewed., Comment: 19 pages, 5 figures v2 improves and somewhat expands the presentation and corrects a typo

Dark matter which scatters off ordinary matter with a relatively large cross section cannot be constrained by deep underground WIMP experiments, due to the energy loss of DM along its path. However, for a sufficiently large cross section, DM particles in the GeV mass range can be captured and thermalized within Earth, resulting in the accumulation of a DM atmosphere whose number density can be as large as $10^{14} \text{ cm}^{-3}$ at Earth's surface. (If the DM-nucleon interaction is attractive and bound states can be formed, most DM bind to nuclei and the density is much lower.) Neufeld and Brach-Neufeld performed experiments to constrain the DM-baryon scattering cross section of DM atmosphere around Earth, by measuring the evaporation rate of liquid nitrogen in a storage dewar within which various materials are immersed. If the DM-nitrogen cross section is in an appropriate range, room temperature DM would penetrate the dewar walls and scatter on the cold nitrogen, increasing its evaporation rate beyond the observed level. Limits on the cross section of DM with other materials than nitrogen are obtained by adding known amounts of different materials; if the material is heated by interactions with DM, that heats and evaporates the liquid nitrogen. Because Born approximation is in general invalid in much of the relevant cross section regime, it is non-trivial to interpret such experimental results as a limit on the DM-nucleon cross section. In this paper we derive the constraints on DM-baryon scattering, with the interaction modeled as a Yukawa potential sourced by the finite sized nucleus. Combining the dewar constraints with BBN, we exclude for the first time a cross section above $10^{-26} \text{ cm}^{2}$ for DM mass 0.8-5.5 GeV, for any sign interaction. One DM model that is constrained is sexaquark $(uuddss)$ DM with mass $m_X \sim 2$ GeV; it remains viable., Comment: 21 pages, 9 figures

We have constructed a catalog of active galactic nuclei (AGNs) with $z < 0.13$, based on optical spectroscopy, from the parent sample of galaxies in the 6dF galaxy survey (Final Release of 6dFGS), a census of the Southern hemisphere. This work is an extension of our all sky AGN catalog \citet [ZCF, here after]{ZCF19}. The ZCF is based on 43,533 galaxies with $\rm K_s \leq$ 11.75 ($z \leq 0.09$) in the 2MASS Redshift Survey (2MRS). The parent catalog of this work, the 6dF catalog, consists of 136,304 publicly available digital spectra for 125,071 galaxies with $\rm Dec \leq 0^\circ$ and $\rm K_s \leq 12.65$ (median $z = 0.053$). Our AGN catalog consists of 3109 broad line AGNs and 12,156 narrow line AGNs which satisfy the \citet{Kauffmann03} criteria, of which 3865 also satisfy the \citet{Kewley01} criteria. We also provide emission line widths, fluxes, flux errors, and signal-to-noise ratios of all the galaxies in our spectroscopic sample, allowing users to customize the selection criteria. In addition, we provide AGN likelihood for the rest of galaxies based on the availability and quality of their spectra. These likelihood values can be used for rigorous statistical analyses., Comment: 19 pages, 16 figures, accepted for publication in ApJS. arXiv admin note: text overlap with arXiv:1902.03799

We present new results on the thermal production yield of a hypothetical state made of six quarks $uuddss$ assuming its production in heavy-ion collisions at the CERN LHC. A state with this quark content and mass low enough to be stable against decay in timescales of the order of the age of the Universe, has been hypothesized by one of us (G.F.) and has been discussed as a possible dark matter candidate. In this work we address for the first time the thermal production rate that can be expected for this state in heavy-ion collisions at colliders. For this estimate we use a thermal model which has been shown to describe accurately the production of hadrons and nuclei in heavy-ion collisions at LHC energy. This estimate is of great relevance for sexaquark searches at colliders as well as for its consideration as a dark matter candidate and for the composition of neutron stars., Comment: 11 pages, 2 figures

We explore inferences on ultrahigh energy cosmic ray (UHECR) source environments -- constrained by the spectrum and composition of UHECRs and non-observation of extremely high energy neutrinos -- and their implications for the observed high energy astrophysical neutrino spectrum. We find acceleration mechanisms producing power-law CR spectra~$\propto E^{-2}$ are compatible with UHECR data, if CRs at high rigidities are in the quasi-ballistic diffusion regime as they escape their source environment. Both gas-dominated and photon-dominated source environments are able to account for UHECR observations, however photon-dominated sources give a better fit. Additionally, gas-dominated sources are in tension with current neutrino constraints. Accurate measurement of the neutrino flux at $\sim 10$ PeV will provide crucial information on the viability of gas-dominated sources, as well as whether diffusive shock acceleration is consistent with UHECR observations. We also show that UHECR sources are able to give a good fit to the high energy portion of the astrophysical neutrino spectrum, above $\sim$ PeV. This common origin of UHECRs and high energy astrophysical neutrinos is natural if air shower data is interpreted with the Sibyll2.3c hadronic interaction model, which gives the best-fit to UHECRs and astrophysical neutrinos in the same part of parameter space, but not for EPOS-LHC.

A rotation curve inequality that holds for spherically symmetric mass distributions is derived, and tested against the SPARC galaxy rotation curves dataset. We identify several Galaxies, eg NGC7793 and UGC05253, which are candidates for hosting non-spherical dark matter structures that could be detected by more precise measurements.

At any epoch, particle physics must be open to completely unexpected discoveries, and that is reason enough to extend the reach of searches for ultra-high energy (UHE) photons. The observation of a population of photons with energies $E \gtrsim 100$ EeV would for example imply the existence of either a completely new physical phenomena, or particle acceleration mechanisms heretofore never seen or imagined. But as we outline in this Letter of Interest, there are also good arguments for super-heavy dark matter (SHDM) in a parameter range such that it could be discovered via its decays to, in particular, UHE photons. Only ultra-high energy cosmic ray observatories have capabilities to detect UHE photons. We first investigate how current and future observations can probe and constrain SHDM models in important directions, and then outline some of the scenarios that motivate such searches. We also discuss connections between constraints on SHDM and on the parameter values of cosmological models., Comment: SNOWMASS 2021 LoI. Accepted for publication in Astroparticle Physics

We use the galaxy rotation curves in the SPARC database to compare 9 different dark matter and modified gravity models on an equal footing, paying special attention to the stellar mass-to-light ratios. We compare three non-interacting dark matter models, a self interacting DM (SIDM) model, two hadronically interacting DM (HIDM) models, and three modified Newtonian dynamics type models: MOND, Radial Acceleration Relation (RAR) and a maximal-disk model. The models with DM-gas interactions generate a disky component in the dark matter, which significantly improves the fits to the rotation curves compared to all other models except an Einasto halo; the MOND-type models give significantly worse fits., Comment: We fixed a typo in eq A3, added fig 6 and updated fig 1 and fig 8 with two galaxy subsets of high and low inclinations

Ultra-high-energy cosmic rays (UHECRs) are atomic nuclei from space with vastly higher energies than any other particles ever observed. Their origin and chemical composition remain a mystery. As we show here, the large- and intermediate-angular-scale anisotropies observed by the Pierre Auger Observatory are a powerful tool for understanding the origin of UHECRs. Without specifying any particular production mechanism, but only postulating that the source distribution follows the matter distribution of the local Universe, a good accounting of the magnitude, direction and energy dependence of the dipole anisotropy at energies above $8 \times 10^{18}$ eV is obtained, after taking into account the impact of energy losses during propagation (the "GZK horizon"), diffusion in extragalactic magnetic field and deflections in the Galactic magnetic field (GMF). This is a major step toward the long-standing hope of using UHECR anisotropies to constrain UHECR composition and magnetic fields. The observed dipole anisotropy is incompatible with a pure proton composition in this scenario. With a more accurate treatment of energy losses, it should be possible to further constrain the cosmic-ray composition and properties of the extragalactic magnetic field, self-consistently improve the GMF model, and potentially expose individual UHECR sources., Comment: Accepted by the Astrophysical Journal Letters

Traditional dark matter models, eg. WIMPs, assume dark matter is weakly coupled to the standard model so that elastic scattering between dark matter and baryons can be described perturbatively by Born approximation. Most direct detection experiments are analyzed according to that assumption. We show that when the fundamental DM-baryon interaction is attractive, dark matter-nucleus scattering is non-perturbative in much of the relevant parameter range. The cross section exhibits rich resonant behavior with a highly non-trivial dependence on atomic mass; furthermore, the extended rather than point-like nature of nuclei significantly impacts the cross sections. The repulsive case also requires full numerical calculation. These non-perturbative effects change existing constraints. Near a resonance value of the parameters, the cross section has non-trivial velocity dependence rather than the usual $\sigma \sim v^0$; we take the velocity dependence into account. (However doing so has little impact on current constraints.) We report the corrected exclusion regions superseding previous limits from XQC, CRESST Surface Run, CMB power spectrum and extensions with Lyman-$\alpha$ and Milky Way satellites, and Milky Way gas clouds. Some limits become weaker than previous bounds in the literature, while others become stronger. Gaps which open by correct treatment of some particular constraint can sometimes be closed using a different constraint. We also discuss the dependence on mediator mass and give approximate expressions for the velocity dependence near a resonance. Sexaquark ($uuddss$) DM with mass around 2 GeV, which exchanges QCD mesons with baryons, remains unconstrained for most of the parameter space of interest. A statement in the literature that a DM-nucleus cross section larger than $10^{-25}\,{\rm cm}^2$ implies dark matter is composite, is corrected., Comment: 31+10 pages,15+3 figures. v2 adds some citations and additional analyses: (1) repulsive as well as attractive interaction, (2) separate analysis of CMB and CMB+Ly-alpha limits & non-trivial role of DM-He scattering relative to Born case, (3) Milky Way gas clouds and Milky Way satellites, (4) velocity dependence near resonances (& approximate analytic expression), (4) dependence on mediator mass

We report on the possibility that the Dark Matter particle is a stable, neutral, as-yet-undiscovered hadron in the standard model. The existence of a compact color-flavor-spin singlet sexaquark (S, uuddss) with mass ~2m_p, is compatible with current knowledge. The S interacts with baryons primarily via a Yukawa interaction of coupling strength alpha_SN, mediated by omega and phi vector mesons having mass ~1 GeV. If it exists, the S is a very attractive DM candidate. The relic abundance of S Dark Matter (SDM) is established when the Universe transitions from the quark-gluon plasma to the hadronic phase at ~150 MeV and is in remarkable agreement with the observed Omega_DM/Omega_b = 5.3+-0.1; this is a no-free-parameters result because the relevant parameters are known from QCD. Survival of this relic abundance to low temperature requires the breakup amplitude gtilde <~ 2 10^-6, comfortably compatible with theory expectations and observational bounds because the breakup amplitude is dynamically suppressed and many orders of magnitude smaller, as we show. The scattering cross section can differ by orders of magnitude from Born approximation, depending on alpha_SN, requiring reanalysis of observational limits. We use direct detection experiments and cosmological constraints to determine the allowed region of alpha_SN. For a range of allowed values, we predict exotic nuclear isotopes at a detectable level with mass offset ~2 amu. The most promising approaches for detecting the sexaquark in accelerator experiments are to search for a long-interaction-length neutral particle component in the central region of relativistic heavy ion collisions or using a beam-dump setup, and to search for evidence of missing particle production characterized by unbalanced baryon number and strangeness using Belle-II or possibly GLUEX at J-Lab., Comment: 25 pp, 13 figs. abstract abbreviated here; FIGURE 2 has been replaced (plotting bug) -- other content is correct and unchanged

Cosmic neutrinos provide a unique window into the otherwise-hidden mechanism of particle acceleration in astrophysical objects. A flux of high-energy neutrinos was discovered in 2013, and the IceCube Collaboration recently reported the likely association of one high-energy neutrino with a flare from the relativistic jet of an active galaxy pointed towards the Earth. However a combined analysis of many similar active galaxies revealed no excess from the broader population, leaving the vast majority of the cosmic neutrino flux unexplained. Here we present the likely association of a radio-emitting tidal disruption event, AT2019dsg, with a second high-energy neutrino. AT2019dsg was identified as part of our systematic search for optical counterparts to high-energy neutrinos with the Zwicky Transient Facility. The probability of finding any coincident radio-emitting tidal disruption event by chance is 0.5%, while the probability of finding one as bright in bolometric energy flux as AT2019dsg is 0.2%. Our electromagnetic observations can be explained through a multi-zone model, with radio analysis revealing a central engine, embedded in a UV photosphere, that powers an extended synchrotron-emitting outflow. This provides an ideal site for PeV neutrino production. Assuming that the association is genuine, our observations suggest that tidal disruption events with mildly-relativistic outflows contribute to the cosmic neutrino flux., Comment: Title and text modified during journal review. Version accepted for publication in Nature Astronomy

We use a multimessenger approach to constrain realistic mixed composition models of ultrahigh energy cosmic ray sources using the latest cosmic ray, neutrino, and gamma-ray data. We build on the successful Unger-Farrar-Anchordoqui 2015 (UFA15) model which explains the shape of the spectrum and its complex composition evolution via photodisintegration of accelerated nuclei in the photon field surrounding the source. We explore the constraints which can currently be placed on the redshift evolution of sources and the temperature of the photon field surrounding the sources. We show that a good fit is obtained to all data either with a source which accelerates a narrow range of nuclear masses or a Milky Way-like mix of nuclear compositions, but in the latter case the nearest source should be 30-50 Mpc away from the Milky Way in order to fit observations from the Pierre Auger Observatory. We also ask whether the data allow for a subdominant purely protonic component at UHE in addition to the primary UFA15 mixed composition component. We find that such a two-component model can significantly improve the fit to cosmic ray data while being compatible with current multimessenger data., Comment: Fixed 26% normalization error, conclusions remain unchanged

The paper "Calorimetric Dark Matter Detection with Galactic Center Gas Clouds" (Bhoonah et al. 2018) aims to derive limits on dark matter interactions by demanding that heat transfer due to DM interactions is less than that by astrophysical cooling, using clouds in the hot, high-velocity nuclear outflow wind of the Milky Way ($T_{wind} \sim 10^{6-7}$ K, $V_{wind} \sim$ 330 km/s). We argue that clouds in such an extreme environment cannot be assumed to be stable over the long timescales associated with their radiative cooling rates. Furthermore, Bhoonah et al. (2018) uses incorrect parameters for their clouds., Comment: 2 pages, 1 figure. Version appearing in Phys. Rev. Lett

We use observations of gas-rich dwarf galaxies to derive constraints on dark matter scattering with ordinary matter. We require that heating/cooling due to DM interacting with gas in the Leo T dwarf galaxy not exceed the ultra-low radiative cooling rate of the gas. This enables us to set $(i)$ stronger bounds than all the previous literature on ultra-light hidden photon DM for nearly all of the mass range $10^{-23}\lesssim m_\mathrm{DM} \lesssim 10^{-10}$ eV, $(ii)$ limits on sub-GeV millicharged DM which add to the constraints on the recent EDGES 21cm absorption anomaly, and $(iii)$ constraints on DM-baryon interactions directly at low relative velocities $v_\mathrm{rel}\sim 17$ km/s. Our study opens a new direction at using observations of gas-rich dwarf galaxies from previous, current and upcoming optical and 21cm surveys to probe physics beyond the standard model., Comment: 5+10 pages, 4+6 figures. Version appearing in PRD. Title and abstract revised to reflect the primary message of the paper. Minor changes to figures, conclusions unchanged. The code associated with this paper is available at https://github.com/JayWadekar/Gas_rich_dwarfs

We explore particle physics beyond accelerator energies, motivated by questions exposed in astroparticle physics observations: 1) Are there reasonable modifications to the standard extrapolations of LHC-tuned hadronic interaction models, so that ultrahigh energy cosmic ray (UHECR) showers are well-described with a purely protonic primary composition rather than requiring a tuned, energy-dependent composition mixture as needed in conventional models? 2) What modifications to standard models can solve the deficiency in the predicted ground signal found in hybrid UHECR observations? We find that a pure proton composition provides an excellent fit to shower observations, if the QCD inelastic cross section increases more rapidly above $E_{\rm cm} \approx 60$ TeV than in conventional models, and speculate as to possible reasons this may happen; the "muon deficiency" can be cured by relatively minor modifications to particle ratios in unexplored kinematic regimes below and above LHC energies., Comment: This paper was prepared for the ISVHECRI 2014 proceedings, but never posted to the arXiv through an oversight. A few relevant subsequent citations have been added

We have constructed an all-sky catalog of optical AGNs with $z < 0.09$, based on optical spectroscopy, from the parent sample of galaxies in the 2MASS Redshift Survey (2MRS), a near-complete census of the nearby universe. Our catalog consists of 1929 broad line AGNs, and 6562 narrow line AGNs which satisfy the \citet{Kauffmann03} criteria, of which 3607 also satisfy the \citet{Kewley01} criteria. We also report emission line widths, fluxes, flux errors, and signal-to-noise ratios of all the galaxies in our spectroscopic sample, allowing users to customize the selection criteria. Although we uniformly processed the spectra of galaxies from a homogeneous parent sample, inhomogeneities persist due to the differences in the quality of the obtained spectra, taken with different instruments, and the unavailability of spectra for $\sim$20\% of the galaxies. We quantify how the differences in spectral quality affect not only the AGN detection rates but also broad line to narrow line AGN ratios. We find that the inhomogeneities primarily stem from the continuum signal-to-noise (S/N) in the spectra near the emission lines of interest. We fit for the AGN fraction as a function of continuum S/N and assign AGN likelihoods to galaxies which were not identified as AGNs using the available spectra. This correction results in a catalog suitable for statistical studies. This work also paves the way for a truly homogeneous and complete nearby AGN catalog by identifying galaxies whose AGN status needs to be verified with higher quality spectra, quantifying the spectral quality necessary to do so., Comment: 30 pages, 24 figures, 5 tables

This document summarises proposed searches for new physics accessible in the heavy-ion mode at the CERN Large Hadron Collider (LHC), both through hadronic and ultraperipheral $\gamma\gamma$ interactions, and that have a competitive or, even, unique discovery potential compared to standard proton-proton collision studies. Illustrative examples include searches for new particles -- such as axion-like pseudoscalars, radions, magnetic monopoles, new long-lived particles, dark photons, and sexaquarks as dark matter candidates -- as well as new interactions, such as non-linear or non-commutative QED extensions. We argue that such interesting possibilities constitute a well-justified scientific motivation, complementing standard quark-gluon-plasma physics studies, to continue running with ions at the LHC after the Run-4, i.e. beyond 2030, including light and intermediate-mass ion species, accumulating nucleon-nucleon integrated luminosities in the accessible fb$^{-1}$ range per month., Comment: 20 pages, 6 figures. Minor updates to match the final version published as JPG 47 (2020) 060501. (A slightly reduced version of this document was submitted as input to the update of the European Particle Physics Strategy EPPS-2019)

We have conducted a study to quantify the systematic differences resulting from using different stellar population models in optical spectroscopic identification of type II AGN. We examined the different AGN detection fractions of 7069 nearby galaxies (z <= 0.09) with SDSS DR8 spectra when using the Bruzual & Charlot (2003, BC03), Vazdekis et al. (2010, MILES), and solar metallicity Maraston and Stromback (2011) (MS11solar) stellar population models. The line fluxes obtained using BC03 and MS11solar are publicly available from SDSS data releases. We find that the BC03 templates result in systematically higher BPT line ratios and consequently higher AGN fractions and the MS11solar templates result in systematically lower line ratios and AGN fractions compared with the MILES templates. Using MILES as the standard, BC03 results in 25% "false positives" and MS11solar results in 22% "false negatives" when using the Kewley et al. (2001a) boundary for AGN identification. The fraction of galaxies whose AGN identification changes for different templates is luminosity dependent, ranging from a few percent for L[OIII]5007 >= 10^40 erg s-1 and increasing to ~ 50% for L[OIII]5007 <= 10^38 erg s-1. These results suggest that template choice should be accounted for when using and comparing the AGN and emission line fluxes from different catalogs., Comment: 21 pages, 20 figures, 1 table; accepted for publication in The Astrophysical Journal

For dark matter (DM) particles with masses in the 0.6 - 6 m_p range, we set stringent constraints on the interaction cross-sections for scattering with ordinary baryonic matter. These constraints follow from the recognition that such particles can be captured by - and thermalized within - the Earth, leading to a substantial accumulation and concentration of DM that interact with baryons. Here, we discuss the probability that DM intercepted by the Earth will be captured, the number of DM particles thereby accumulated over Earth's lifetime, the fraction of such particles retained in the face of evaporation, and the density distribution of such particles within the Earth. In the latter context, we note that a previous treatment of the density distribution of DM, presented by Gould and Raffelt and applied subsequently to DM in the Sun, is inconsistent with considerations of hydrostatic equilibrium. Our analysis provides an estimate of the DM particle density at Earth's surface, which may exceed 1.E+14 cm-3 for the mass range under consideration. Based upon our determination of the DM density at Earth's surface, we derive constraints on the scattering cross-sections. These constraints are placed by four considerations: (1) the lifetime of the relativistic proton beam at the Large Hadron collider (LHC); (2) the orbital decay of spacecraft in low Earth orbit (LEO); (3) the vaporization rate of cryogenic liquids in well-insulated storage dewars; and (4) the thermal conductivity of Earth's crust. As an example application of our results, we show that for the scattering cross-sections that were invoked recently in Barkana's original explanation for the anomalously deep 21 cm absorption reported by EDGES, DM particle masses in the 0.6 - 4 m_p range are ruled out., Comment: Accepted for publication in ApJ. This version has several minor changes to improve clarity. A new appendix had been added to justify our treatment of the dark matter density distribution within the Earth, where we note that a previous analysis of the density distribution of DM in the Sun by Gould and Raffelt is inconsistent with considerations of hydrostatic equilibrium

If dark matter (DM) contains equal numbers of u,d,s quarks, the ratio of DM and ordinary matter densities is shown to follow from the Boltzmann distribution in the Quark Gluon Plasma. For sexaquark DM in the 1860-1880 MeV mass range (assuring sexaquark and nuclear stability) and quark masses and transition temperature from lattice QCD, the observed Omega_{DM}/Omega_b = 5.3 is in the predicted range, with <~ 15% uncertainty. The prediction is insensitive to the current form of DM, which could be sexaquarks, strange quark matter nuggets, primordial black holes from their collapse, or a mixture of these., Comment: v3: Fig. 2 is replaced, correcting a plotting bug. v2: Reorganizes to improve clarity, adds discussion of detection constraints; shows that the small breakup cross section required for survival below T=150 degrees is compatible with expectations. Thus the claim by Kolb and Turner that dibaryons cannot be the dark matter does not appoy to the proposed sexaquark dark matter model

We derive constraints on a possible velocity-dependent DM-nucleon scattering cross section, for Dark Matter in the 10 MeV -- 100 GeV mass range, using the XQC, DAMIC, and CRESST 2017 Surface Run experiments. We report the limits on cross sections of the form $\sigma=\sigma_0\,v^n$, for a range of velocity dependencies with $n\in\{-4,-2,-1,0,1,2\}$. We point out the need to measure the efficiency with which nuclear recoil energy in the sub-keV range thermalizes, rather than being stored as Frenkel pairs in the semi-conductor lattice. The possibility of a significant inefficiency leaves open a considerable `hole' in the limits for mass in the $\sim$ 0.2 -- 2 GeV range, which XQC and CRESST can potentially fill when the thermalization efficiency is measured. We call attention to the asymmetry between a conventional lower limit cross section and the `upper-reach cross section' imposed by attenuation in an overburden -- an upper boundary being extremely sharp but quite insensitive to the statistics of the experiment. Considering the recent interest to use dark matter-baryon interaction with velocity dependence $n=-4$ to explain the EDGES 21 cm anomaly, we also derive the limits on milli-charged DM that scatters off protons and electrons under a Coulomb-like interaction. We find that much but not all of the region of interest for the EDGES anomaly can be excluded., Comment: 34 pages, 9 figures, 5 tables. v3: Matches version accepted to JCAP

The relationship between the populations of optically and X-ray selected Active Galactic Nuclei (AGN) has been unclear due to divergent results from different studies. Arnold et al. (2009) claim that X-ray AGN are almost entirely disjoint from optical AGN, while the Swift-BAT 70-month hard X-ray survey reported that 553 of their 711 X-ray AGN are optical. In this work, we set out to understand this difference by cross-checking between these studies and examining their sampling and AGN-selection criteria. We also re-analyze the X-ray and optical AGN in 16 groups and clusters reported by Arnold et al. using our own optical spectrum fitting techniques. We find that 6 of the 8 X-ray AGN in the Arnold et al. sample are also optical AGN, contrary to Arnold et al.'s report that only 1 of the 8 X-ray AGN is also an optical AGN, thereby falsifies their conclusion that optical and X-ray AGN are nearly disjoint sets.

As experimental constraints on DM interactions become ever more sensitive and push into new regimes of DM mass, it becomes more and more challenging to accurately model the process by which Dark Matter particles lose energy through scattering in the Earth's surface or other overburdens. We show that a commonly-used approximation due to Starkman, Gould, Esmailzadeh and Dimopoulos (SGED) can fail badly in computing the attenuation, even while being useful for an order-of-magnitude estimate of the maximum cross section reach. We introduce a method of importance sampling which makes Monte-Carlo simulation of energy loss feasible, in spite of factor-$10^7$ or greater attenuation. We demonstrate the validity of our new method and expose multiple problems with the SGED approximation, this reveals interesting features of the energy loss process. We spot-check the recent Emken, Kouvaris and Shoemaker "$5\,\Delta v$" prescription to place limits on cross sections based on a limited-statistics analysis, and find that an accurate simulation yields a factor of $\rm{4.4\times10^6}$ and $\rm{2.4\times10^4}$ larger number of events, for 50 MeV and 1 GeV DM mass respectively, than if the EKS $5\,\Delta v$ prescription were valid.

It has recently been proposed that the relatively inert, highly symmetric, neutral flavor singlet scalar hadron made of uuddss quarks may have a mass < 2 (m_p + m_e). This is consistent with QCD theory, and with existing accelerator and non-accelerator constraints. For mass in the 1.5-1.8 GeV range, the observed DM relic abundance and the observed DM to ordinary matter ratio can emerge naturally. Dark matter freezes out before primordial nucleosynthesis and does not significantly impact primordial abundances, so the conventional argument that DM is non-baryonic does not apply. The interaction cross section between DM and the gas in the Galaxy is such that the dark matter in our local neighborhood is naturally co-rotating with the solar system, to a sufficient degree that DM may not have enough energy to be detected in applicable DM experiments. Interaction with the gas in galactic disks provides the first (non-MONDian) explanation for the striking correlation in the small-scale structure of rotation curves and the inhomogeneous distribution of gas, and also accounts (unlike MOND) for instances of galaxies not exhibiting such correlations. Depending on the cross-section, a DM-baryon interaction can produce a dark matter disk as suggested by recent studies, and has many or all virtues of self-interacting DM (SIDM) for removing inconsistencies of LCDM. Lab experiments to discover this particle are discussed., Comment: Talk at ICRC 2017, Busan, S. Korea, Jul 2017, 8pp; v2 corrects latex error which cropped x-axis label on Fig 1. No other changes

We report results of the first comprehensive, high resolution study of the deflections of UHECRs using a realistic model of the Galactic magnetic field and extending to sufficiently low rigidities, R = E/Z = 10^18 V, to describe Fe in the UHE energy range or the mixed composition reported by the Pierre Auger Collaboration at the energy of the observed dipole anisotropy. We use the Jansson-Farrar (JF12) model, which has both large scale coherent and a structured random components, and determine deflections for fifteen rigidities from 10^18.0 to 10^20.0 V, for L_coh = 30 pc and 100 pc. We check the sensitivity of UHECR deflections to the particular realization of the random field, for 3 rigidity values. For each rigidity and field model studied, the UHECR arrival direction distribution is determined for an arbitrary source direction, by inverting the trajectories of > 5 x 10^7 isotropic anti-CRs of the given rigidity. We present skyplots and tables characterizing the arrival directions, for representative 1 deg sources. Except at high rigidity, the pattern of multiple images is very complex and depends strongly on the coherence length and source direction. For almost all sources, average deflections grow rapidly as the rigidity falls below 10 EV and deflections commonly are greater than 90 deg. Magnification and demagnification can be strong at almost all rigidities, and varies significantly with source direction. Much of the extragalactic celestial sphere, behind and south of the Galactic Center, cannot be seen in UHECRs below 10 EV. The pattern of deflections obtained with the coherent field alone can be significantly different than with the complete field model, even as regards the position of the centroid, for some source directions and rigidities. Multiple images, sometimes very widely separated, are common for small coherence length, especially for low rigidity., Comment: 53 pp, many figures. Figures have been compressed to reduce file size; uncompressed figures available on request

We improve limits on the spin-independent scattering cross section of Dark Matter on nucleons, for DM in the 300 MeV -- 100 GeV mass range, based on the DAMIC and XQC experiments. Our results close the window which previously existed in this mass range, for a DM-nucleon cross section of order $\approx \mu$b, assuming the standard velocity distribution., Comment: 23 pages, 15 figures. v3: Matches version accepted to JCAP

It is proposed that the neutral, B=2, flavor singlet sexaquark (S) composed of uuddss quarks, has mass m_S <~ 2 GeV. If m_S < 2 (m_p + m_e), it is absolutely stable, while for m_S < m_p+m_e + m_Lambda, its lifetime can be greater than the age of the Universe. Lattice gauge theory cannot yet predict m_S, but indirect evidence supports the hypothesis of stability. A stable S is consistent with QCD theory and would have eluded detection in accelerator and non-accelerator experiments. If it exists, the S is a good Dark Matter candidate. Analyses of existing Upsilon decay and LHC data can be used to discover it and measure its mass., Comment: v2: added new sections in Supplementary Materials on naming and Belz et al experiment; added some clarifying material and streamlined elsewhere; updated references

We improve on the model of the Galactic Magnetic Field (GMF) from Jansson \& Farrar (2012), which was constrained using all-sky rotation measures of extragalactic sources and polarized and unpolarized synchrotron emission data from WMAP. We have developed several alternative functional forms for the coherent and random components, used newer synchrotron products from Planck and WMAP and testes new models of the densities of thermal electrons and cosmic-ray electrons. The differences in the resultant GMF models, depending on which parameterization of the field, synchrotron product and electron densities are used, provides a measure of the uncertainty in our inference of the GMF. We discuss the impact of these uncertainties on charged-particle astronomy at ultra-high energies., Comment: 8 pages, 2 figures, to appear in the Proceedings of the 35th International Cosmic Ray Conference 10-20 July, 2017 Bexco, Busan, Korea

Studies discerning whether there is a significant correlation between UHECR arrival directions and optical AGN are hampered by the lack of a uniformly selected and complete all-sky optical AGN catalog. To remedy this, we are preparing such a catalog based on the 2MASS Redshift Survey (2MRS), a spectroscopic sample of $\sim 44,500$ galaxies complete to a K magnitude of 11.75 over 91% of the sky. We have analyzed the available optical spectra of these 2MRS galaxies ($\sim 80$% of the galaxies), in order to identify the AGN amongst them with uniform criteria. We present a first-stage release of the AGN catalog for the southern sky, based on spectra from the 6dF Galaxy survey and CTIO telescope. Providing a comparably uniform and complete catalog for the northern sky is more challenging because the spectra for the northern galaxies were taken with different instruments., Comment: 8 pages, 5 figures, Proceedings of The 34th International Cosmic Ray Conference

The sharp change in slope of the ultra-high energy cosmic ray (UHECR) spectrum around 10^{18.6} eV (the ankle), combined with evidence of a light but extragalactic component near and below the ankle which evolves to intermediate composition above, has proved exceedingly challenging to understand theoretically. We show that for a range of source conditions, photo-disintegration of ultra-high energy nuclei in the region surrounding a UHECR accelerator naturally accounts for the observed spectrum and composition of the entire extragalactic component, which dominates above about 10^{17.5} eV. The mechanism has a clear signature in the spectrum and flavors of neutrinos., Comment: Contribution to ICRC 2015. Full exposition (Unger, Farrar and Anchordoqui, accepted for Phys. Rev. D) can be found in arXiv:1505.02153

It has long been recognized that magnetic fields play an important role in many astrophysical environments, yet the strength and structure of magnetic fields beyond our solar system have been at best only qualitatively constrained. The Galactic magnetic field in particular is crucial for modeling the transport of Galactic CRs, for calculating the background to dark matter and CMB-cosmology studies, and for determining the sources of UHECRs. This report gives a brief overview of recent major advances in our understanding of the Galactic magnetic field (GMF) and its lensing of Galactic and ultrahigh energy cosmic rays., Comment: Invited talk at the Focus Meeting on Scale Free Phenomena at the Honolulu IAU, Aug. 2015. arXiv admin note: substantial text overlap with arXiv:1508.04530

A good model of the Galactic magnetic field is crucial for estimating the Galactic contribution in dark matter and CMB-cosmology studies, determining the sources of UHECRs, and also modeling the transport of Galactic CRs since the halo field provides an important escape route for by diffusion along its field lines. We briefly review the observational foundations of the Jansson-Farrar 2012 model for the large scale structure of the GMF, underscoring the robust evidence for a N-to-S directed, spiraling halo field. New results on the lensing effect of the GMF on UHECRs are presented, displaying multiple images and dramatic magnification and demagnification that varies with source direction and CR rigidity., Comment: Oral Contribution to ICRC 2015

The sharp change in slope of the ultrahigh energy cosmic ray (UHECR) spectrum around 10^18.6 eV (the ankle), combined with evidence of a light but extragalactic component near and below the ankle and intermediate composition above, has proved exceedingly challenging to understand theoretically, without fine-tuning. We propose a mechanism whereby photo-disintegration of ultrahigh energy nuclei in the region surrounding a UHECR accelerator accounts for the observed spectrum and inferred composition at Earth. For suitable source conditions, the model reproduces the spectrum and the composition over the entire extragalactic cosmic ray energy range, i.e. above 10^17.5 eV. Predictions for the spectrum and flavors of neutrinos resulting from this process are also presented., Comment: extended discussion of source parameters, accepted for publication in PRD