Search

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., 21 pages, 9 figures

The Pierre Auger Observatory, located in western Argentina, is the world's largest cosmic-ray observatory. While it was originally built to study the cosmic-ray flux above $10^{18.5}~$eV, several enhancements have reduced this energy threshold. One such enhancement is a surface array composed of a triangular grid of $19$ water-Cherenkov detectors separated by $433~$m (SD-433) to explore the energies down to about $10^{16}~$eV. We are developing two research lines employing the SD-433. Firstly, we will measure the energy spectrum in a region where previous experiments have shown evidence of the second knee. Secondly, we will search for ultra-high energy photons to study PeV cosmic-ray sources residing in the Galactic center. In this work, we introduce the SD-433 and we show that it is fully efficient above $5\times 10^{16}~$eV for hadronic primaries with $\theta < 45^\circ$. Using seven years of data, we present the parametrization of the lateral distribution function of measured signals. Finally, we show that an angular resolution of $1.8^\circ$ ($0.5^\circ$) can be attained at the lowest (highest) primary energies. Our study lays the goundmark for measurements in the energy range above $10^{16}~$eV by utilizing the SD-433 and thus expanding the scientific output of the Auger surface detector.

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., 2 pages, 1 figure. Version appearing in Phys. Rev. Lett

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)

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., 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 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

Observations of the spectacular, blazar-like tidal disruption event (TDE) candidates Swift J1644+57 and J2058+05 show that the conditions required for accelerating protons to 10^{20} eV appear to be realized in the outer jet, and possibly in the inner jet as well. Direct and indirect estimates of the rate of jetted-TDEs, and of the energy they inject, are compatible with the observed flux of ultra-high energy cosmic rays (UHECRs) and the abundance of presently contributing sources. Thus TDE-jets can be a major source of UHECRs, even compabile with a pure proton composition.

Four UHECRs in the combined HiRes and AGASA datasets are backtracked in the Galactic magnetic field. They point to a common source which is localized to within 1 degree, if they are protons as is shown to be the most probable charge assignment. A Swift-BAT hard X-ray AGN in the galaxy CGCG 291-028 is the only notable source candidate within the source locus and within the GZK distance horizon. The spectrum of the four events is consistent with production in a transient event such as a stellar tidal disruption flare. Under the assumption the UHECRs were produced in CGCG 291-028, the total energy of UHECRs produced by the transient can be estimated and extragalactic magnetic deflections can be constrained. If CGCG 291-028 is indeed the source of the UHECRs, observations of its present state should elucidate the phenomenon of UHECR acceleration., 4 pages; contribution to ICRC 2013; v1 was an incomplete draft submitted in error; v2 is the correct version

We summarize the remarkable recent progress in ultra-high energy cosmic ray physics and astronomy enabled by the current generation of cosmic ray observatories. We discuss the primary objectives for future measurements and describe the plans for near-term enhancements of existing experiments as well as the next generation of observatories., 7 revtex pages, 1 figure (v2 author added, references added)

We report on Chandra X-ray observations of possible-AGNs which have been correlated with Ultra-high Energy Cosmic Rays (UHECRs) observed by the Pierre Auger Collaboration. Combining our X-ray observations with optical observations, we conclude that one-third of the 21 Veron-Cetty Veron (VCV) galaxies correlating with UHECRs in the first Auger data-release are actually not AGNs. We review existing optical observations of the 20 VCV galaxies correlating with UHECRs in the second Auger data-release and determine that three of them are not AGNs and two are uncertain. Overall, of the 57 published UHECRs with |b|>10 degrees, 22 or 23 correlate with true AGNs using the Auger correlation parameters. We also measured the X-ray luminosity of ESO139-G12 to complete the determination of the bolometric luminosities of AGNs correlating with UHECRs in the first data-set. Apart from two candidate sources which require further observation, we determined bolometric luminosities for the candidate galaxies of the second dataset. We find that only two of the total of 69 published UHECRs correlate with AGNs (IC5135 and IC4329a) which are powerful enough in their steady-state to accelerate protons to the observed energies of their correlated UHECRs. The GZK expectation is that about 45% of the sources of UHECRs above 60 EeV should be contained within the z, ApJ in press; extends and supersedes arXiv:1109.0267. arXiv admin note: substantial text overlap with arXiv:1109.0267

The Auger observatory has observed a possible correlation between Ultrahigh Energy Cosmic Rays (UHECRs) above 57 EeV and nearby candidate Active Galactic Nuclei (AGN) from the Veron-Cetty Veron catalog (VCV). In this paper we report on Chandra X-ray observations of 10 unconfirmed VCV AGN-candidates and luminous IR galaxies correlating with the first set of Auger UHECRs, to determine whether or not they have active nuclei. The X-ray data, when combined with optical luminosities, show that in fact none of the 10 galaxies have a significant AGN component; if there is any nuclear activity at all, it is weak rather than obscured. This reduces the number of UHECRs in the original Auger dataset possibly correlating with AGNs from 20 of 27 down to 14 of 27. We also used Chandra to measure the X-ray luminosity of ESO 139-G12, an AGN which correlates with 2 of the Auger UHECRs, to obtain the first estimate of its bolometric luminosity; this completes the determination of the bolometric luminosities of all correlating AGNs. Taking our results into account, only one of the 27 UHECRs in the original Auger data-release is correlated on a few-degree angular scale with an identified AGN that is powerful enough in its steady-state to accelerate protons to the observed energies, according to conventional acceleration mechanisms. Intriguingly, approximately 60% of the UHECRs with $|b|>10^\circ$ do correlate with genuine AGNs, but these are too weak to meet the acceleration criterion for protons; this may be an indication that AGNs experience transient high-luminosity states which can accelerate UHECRs. To determine the source(s) and composition of UHECRs through statistical correlation studies requires reliable, complete and uniform catalogs of identified AGNs; our a posteriori inspection of ambiguous source candidates underscores the inadequacies of the VCV catalog in this respect., 7 pages, 1 figure

We show that a recently proposed solution to the Hierarchy Problem simultaneously solves the Strong CP Problem, without requiring an axion or any further new physics. Consistency of black hole physics implies a non-trivial relation between the number of particle species and particle masses, so that with ~10^{32} copies of the standard model, the TeV scale is naturally explained. At the same time, as shown here, this setup predicts a typical expected value of the strong-CP parameter in QCD of theta ~ 10^{-9}. This strongly motivates a more sensitive measurement of the neutron electric dipole moment., 8 pp

The angular clustering of 5 Ultrahigh Energy Cosmic Rays (UHECRs) in the combined published AGASA-HiRes data has a probability of ~ 2 10^-3 of occurring by chance. A first analysis of the implications of the event energies and angular spreading is presented, which is applicable if the source is close enough that GZK losses can be ignored. Under this assumption, the observed energies of the events in this cluster favor a bursting rather than continuously emitting source, with the events emitted on a time scale short compared with 300 D_Mpc years. Assuming the UHECRs experience many incoherent small magnetic deflections enroute from source to Earth, the arrival direction distribution allows estimation that < B^2 lambda > D ~ 7.7 nG^2 Mpc^2, where lambda is the coherence length of the field and D is the source distance. If the spectrum at the source ~ E^{-2}, the total isotropic equivalent energy emitted in UHECRs is > 10^43 D_Mpc^3 ergs., Talk at the ICRC07, 4 pp

We give the first detailed study of the arrival time distribution of nucleons in UHECR air showers. We analyze in detail the influence of late arriving particles on the energy determination of the AGASA experiment, as well as how the arrival time distribution changes with distance from shower core. Our calculations are consistent with experimental observations of the AGASA group. Crucial to obtaining agreement, is the correct implementation of the energy loss for low-energy protons. We confirm AGASA's estimation of the error in their energy determination associated with late-arriving particles, assuming primary protons., 8 pages 11 figures

Spergel and Steinhardt have recently proposed the concept of dark matter with strong self-interactions as a means to address numerous discrepancies between observations of dark matter halos on subgalactic scales and the predictions of the standard collisionless dark matter picture. We review the motivations for this scenario and discuss some recent, successful numerical tests. We also discuss the possibility that the dark matter interacts strongly with ordinary baryonic matter, as well as with itself. We present a new analysis of the experimental constraints and re-evaluate the allowed range of cross-section and mass., 12 pages, 3 figures; minor typos corrected. To appear in Proceedings of Dark Matter 2000

An attractive class of SUSY-breaking mechanisms predicts a photino mass of order 1 GeV. Relic photinos can naturally account for the observed dark matter. Detection of these light photinos is discussed and contrasted with conventional WIMPs. In this scenario the gluino mass is about 100 MeV. The lightest gluino-containing baryon could account for the recently observed ultra-high energy cosmic rays, which violate the GZK bound., Invited talk IDM96, Sheffield, England, Sept. 1996. 7 pages with 2 figs, latex

We solve the coupled Boltzmann equation for the system of light photinos interacting with pions and $R^0$'s (the gluon-gluino bound state) to determine the relic abundance of light photinos in the light gaugino scenario. Cosmology bounds the ratio r of the R^0 mass to the photino mass to be less than about 1.8. We also use a model Lagrangian embodying crossing symmetry between the $R^0 \leftrightarrow \photino \pi \pi$ and $R^0 \pi \leftrightarrow \photino \pi$ reactions to identify cosmologically favored regions of $R^0$ lifetime as a function of $R^0$ and photino masses., Comment: 29 page LaTeX file with 6 postscript figures included with epsf

The tree-level-massless gaugino scenario predicts that the lighter chargino mass is less than m_W and that gluino and lightest neutralino masses are $\lsi 1$ GeV. In this case the dominant decay mode of charginos and non-LSP neutralinos is generically to three jets. The excess of "4j" events with total invariant mass $\sim 105$ GeV observed in LEP running at 130-136 GeV is noted to be consistent with pair production of $\sim 53$ GeV charginos. Data at 161 and 172 GeV from Fall, 1996, cannot conclusively test this hypothesis (because cuts to eliminate $W^+W^-$ background reduce the efficiency significantly) but is suggestive that the signal persists., Invited talk at ICHEP96, Warsaw, July, 1996. Based on contributed paper pa11-048 and RU-96-71 (hep-ph/9608387)

The gluonic widths of four leading glueball candidates are determined from their production in radiative quarkonium decays, allowing quantitative estimation of their glue content. Lattice predictions for the scalar and tensor channels seem to be in reasonable agareement with present data (allowing for mixing with $q \bar{q}$ states). However there is a glueball-like-state in the pseudoscalar spectrum whose mass is considerably lower than expected from lattice estimates., Invited talk ICHEP96, Warsaw, Poland, July 29, 1996 based on work done in collaboration with M. B. Cakir, F. E. Close and Z. P. Li

The light gaugino scenario predicts that the lighter chargino mass is less than m_W, gluino and lightest neutralino masses are, Comment: 12 pages, 1 fig.

When SUSY breaking produces only dimension-2 operators, gluino and photino masses are of order 1 GeV or less. The gluon-gluino bound state has mass 1.3-2.2 GeV and lifetime > 10^{-5} - 10^{-10} s. This range of mass and lifetime is largely unconstrained because missing energy and beam dump techniques are ineffective. With only small modifications, upcoming K^0 decay experiments can study most of the interesting range. The lightest gluino-containing baryon (uds-gluino) is long-lived or stable; experiments to find it and the uud-gluino are also discussed., 13 pp, 1 figure (uuencoded). Descendant of hep-ph/9504295, hep-ph/9508291, and hep-ph/9508292, focused on experimental search techniques. To be published in Phys Rev Lett

When SUSY breaking produces only dimension-2 terms in the minimal supersymmetric standard model, the parameters of the theory can be rather well constrained. This paper deals with strategies for the detection of the new hadrons predicted in the 1-3 GeV mass range. Some limits are obtained. New signatures for squarks are also given. Squark masses as small as 45 GeV are not yet excluded., latex, 16pp+2figs

Recent papers by Gavela et al. and Huet et al. claim to have shown that incluion of higher order interactions between quasiparticles dramatically decreases the baryon asymmetry of the universe which can arise in the Minimal Standard Model. These papers employ an inconsistent calculational scheme which, for instance, violates unitarity. We argue that their method cannot be considered as reliable, and thus their conclusions cannot be considered as justified. Recent papers by Gavela et al. and Huet et al. claim to have shown that incluion of higher order interactions between quasiparticles dramatically decreases the baryon asymmetry of the universe which can arise in the Minimal Standard Model. These papers employ an inconsistent calculational scheme which, for instance, violates unitarity. We argue that their method cannot be considered as reliable, and thus their conclusions cannot be considered as justified. Recent papers by Gavela et al. and Huet et al. claim to have shown that incluion of higher order interactions between quasiparticles dramatically decreases the baryon asymmetry of the universe which can arise in the Minimal Standard Model. These papers employ an inconsistent calculational scheme which, for instance, violates unitarity. We argue that their method cannot be considered as reliable, and thus their conclusions cannot be considered as justified. Recent papers by Gavela et al. and Huet et al. claim to have shown that incluion of higher order interactions between quasiparticles dramatically decreases the baryon asymmetry of the universe which can arise in the Minimal Standard Model. These papers employ an inconsistent calculational scheme which, for instance, violates unitarity. We argue that their method cannot be considered as reliable, and thus their conclusions cannot be considered as justified.