109 research outputs found
Novel dark matter constraints from antiprotons in the light of AMS-02
We evaluate dark matter (DM) limits from cosmic-ray antiproton observations
using the recent precise AMS-02 measurements. We properly take into account
cosmic-ray propagation uncertainties fitting at the same time DM and
propagation parameters, and marginalizing over the latter. We find a
significant (~4.5 sigma) indication of a DM signal for DM masses near 80 GeV,
with a hadronic annihilation cross-section close to the thermal value, sigma v
~3e-26 cm3s-1. Intriguingly, this signal is compatible with the DM
interpretation of the Galactic center gamma-ray excess. Confirmation of the
signal will require a more accurate study of the systematic uncertainties,
i.e., the antiproton production cross-section, and modelling of the solar
modulation effect. Interpreting the AMS-02 data in terms of upper limits on
hadronic DM annihilation, we obtain strong constraints excluding a thermal
annihilation cross-section for DM masses below about 50 GeV and in the range
between approximately 150 and 500 GeV, even for conservative propagation
scenarios. Except for the range around 80 GeV, our limits are a factor 4
stronger than the limits from gamma-ray observations of dwarf galaxies.Comment: 6 pages + 3 of supplemental material, 7 figures, 1 tables. Matches
version published on physical review letter
Prospects to verify a possible dark matter hint in cosmic antiprotons with antideuterons and antihelium
Cosmic rays are an important tool to study dark matter annihilation in our
Galaxy. Recently, a possible hint for dark matter annihilation was found in the
antiproton spectrum measured by AMS-02, even though the result might be
affected by theoretical uncertainties. A complementary way to test its dark
matter interpretation would be the observation of low-energy antinuclei in
cosmic rays. We determine the chances to observe antideuterons with GAPS and
AMS-02, and the implications for the ongoing AMS-02 antihelium searches. We
find that the corresponding antideuteron signal is within the GAPS and AMS-02
detection potential. If, more conservatively, the putative signal was
considered as an upper limit on DM annihilation, our results would indicate the
highest possible fluxes for antideuterons and antihelium compatible with
current antiproton data.Comment: 11 pages, 5 figures, matches published versio
Prescriptions on antiproton cross section data for precise theoretical antiproton flux predictions
After the breakthrough from the satellite-borne PAMELA detector, the flux of
cosmic-ray (CR) antiprotons has been provided with unprecedented accuracy by
AMS-02 on the International Space Station. Its data spans an energy range from
below 1 GeV up to 400 GeV and most of the data points contain errors below the
amazing level of 5%. The bulk of the antiproton flux is expected to be produced
by the scatterings of CR protons and helium off interstellar hydrogen and
helium atoms at rest. The modeling of these interactions, which requires the
relevant production cross sections, induces an uncertainty in the determination
of the antiproton source term that can even exceed the uncertainties in the CR
data itself. The aim of the present analysis is to determine the
uncertainty required for cross section
measurements such that the induced uncertainties on the flux are at
the same level. Our results are discussed both in the center-of-mass reference
frame, suitable for collider experiments, and in the laboratory frame, as
occurring in the Galaxy. We find that cross section data should be collected
with accuracy better that few percent with proton beams from 10 GeV to 6 TeV
and a pseudorapidity ranging from 2 to almost 8 or, alternatively, with
from 0.04 to 2 GeV and from 0.02 to 0.7. Similar considerations
hold for the He production channel. The present collection of data is far
from these requirements. Nevertheless, they could, in principle, be reached by
fixed target experiments with beam energies in the reach of CERN accelerators.Comment: 15 pages, 13 figures, matches published versio
Probing dark matter annihilation in the Galaxy with antiprotons and gamma rays
A possible hint of dark matter annihilation has been found in Cuoco,
Korsmeier and Kr\"amer (2017) from an analysis of recent cosmic-ray antiproton
data from AMS-02 and taking into account cosmic-ray propagation uncertainties
by fitting at the same time dark matter and propagation parameters. Here, we
extend this analysis to a wider class of annihilation channels. We find
consistent hints of a dark matter signal with an annihilation cross-section
close to the thermal value and with masses in range between 40 and 130 GeV
depending on the annihilation channel. Furthermore, we investigate in how far
the possible signal is compatible with the Galactic center gamma-ray excess and
recent observation of dwarf satellite galaxies by performing a joint global fit
including uncertainties in the dark matter density profile. As an example, we
interpret our results in the framework of the Higgs portal model.Comment: 12 pages + references, 4 figures, v2: References added, minor changes
in presentation, matches journal versio
Constraining heavy dark matter with cosmic-ray antiprotons
Cosmic-ray observations provide a powerful probe of dark matter annihilation
in the Galaxy. In this paper we derive constraints on heavy dark matter from
the recent precise AMS-02 antiproton data. We consider all possible
annihilation channels into pairs of standard model particles. Furthermore, we
interpret our results in the context of minimal dark matter, including
higgsino, wino and quintuplet dark matter. We compare the cosmic-ray antiproton
limits to limits from -ray observations of dwarf spheroidal galaxies
and to limits from -ray and -line observations towards the
Galactic center. While the latter limits are highly dependent on the dark
matter density distribution and only exclude a thermal wino for cuspy profiles,
the cosmic-ray limits are more robust, strongly disfavoring the thermal wino
dark matter scenario even for a conservative estimate of systematic
uncertainties.Comment: 14 pages + references, 5 figures; v2: HESS limits added in Fig. 2,
matches published versio
Production cross sections of cosmic antiprotons in the light of new data from the NA61 and LHCb experiments
The cosmic-ray flux of antiprotons is measured with high precision by the
space-borne particle spectrometers AMS-02.Its interpretation requires a correct
description of the dominant production process for antiprotons in our Galaxy,
namely, the interaction of cosmic-ray proton and helium with the interstellar
medium. In the light of new cross section measurements by the NA61 experiment
of and the first ever measurement of by the LHCb experiment, we update the
parametrization of proton-proton and proton-nucleon cross sections.We find that
the LHCb He data constrain a shape for the cross section at high energies
and show for the first time how well the rescaling from the channel
applies to a helium target. By using , He and C data we estimate the
uncertainty on the Lorentz invariant cross section for . We use these new cross sections to compute the source
term for all the production channels, considering also nuclei heavier than He
both in cosmic rays and the interstellar medium. The uncertainties on the total
source term are at the level of % and slightly increase below antiproton
energies of 5 GeV. This uncertainty is dominated by the cross section, which translates into all channels since we derive
them using the cross sections. The cross sections to calculate the source
spectra from all relevant cosmic-ray isotopes are provided in the Supplemental
Material. We finally quantify the necessity of new data on antiproton
production cross sections, and pin down the kinematic parameter space which
should be covered by future data.Comment: 16 pages, 11 figures, matches published versio
Cross-calibration of the Transition Radiation Detector of AMS-02 for an Energy Measurement of Cosmic-Ray Ions
Since May 2011 the AMS-02 experiment is installed on the International Space
Station and is observing cosmic radiation. It consists of several
state-of-the-art sub-detectors, which redundantly measure charge and energy of
traversing particles. Due to the long exposure time of AMS-02 of many years the
measurement of momentum for protons and ions is limited systematically by the
spatial resolution and magnetic field strength of the silicon tracker. The
maximum detectable rigidity for protons is about 1.8~TV, for helium about
3.6~TV. We investigate the possibility to extend the range of the energy
measurement for heavy nuclei () with the transition radiation detector
(TRD). The response function of the TRD shows a steep increase in signal from
the level of ionization at a Lorentz factor of about 500 to
, where the transition radiation signal saturates. For
heavy ions the signal fluctuations in the TRD are sufficiently small to allow
an energy measurement with the TRD beyond the limitations of the tracker. The
energy resolution of the TRD is determined and reaches a level of about 20\%
for boron (). After adjusting the operational parameters of the TRD a
measurement of boron and carbon could be possible up to 5~TeV/nucleon.Comment: Accepted for publication in Advances in Space Researc
Implications of Lithium to Oxygen AMS-02 spectra on our understanding of cosmic-ray diffusion
We analyze recent AMS-02 comic-ray measurements of Lithium, Beryllium, Boron,
Carbon, Nitrogen and Oxygen. The emphasis of the analysis is on systematic
uncertainties related to propagation and nuclear cross-sections. To investigate
the uncertainties in the propagation scenario, we consider five different
frameworks, differing with respect to the inclusion of a diffusion break at few
GVs, the presence of reacceleration, and the presence of a break in the
injection spectra of primaries. For each framework we fit the diffusion
equations of cosmic rays and exploring the parameter space with Monte Carlo
methods. At the same time, the impact of the uncertainties in the nuclear
production cross-sections of secondaries is explicitly considered and included
in the fit through the use of nuisance parameters. We find that all the
considered frameworks are able to provide a good fit. In particular, two
competing scenarios, one including a break in diffusion but no reacceleration
and the other with reacceleration but no break in diffusion are both allowed.
The inclusion of cross-section uncertainties is, however, crucial, to this
result. Thus, at the moment, these uncertainties represent a fundamental
systematic preventing a deeper understanding of the properties of CR
propagation. We find, nonetheless, that the slope of diffusion at intermediate
rigidities is robustly constrained in the range in
models without convection, or if convection is included
in the fit. Furthermore, we find that the use of the AMS-02 Beryllium data
provides a lower limit on the vertical size of the Galactic propagation halo of
kpc.Comment: 23 pages, 10 figure
Testing the universality of cosmic-ray nuclei from protons to oxygen with AMS-02
The AMS-02 experiment has provided high-precision measurements of several
cosmic-ray (CR) species. The achieved percent-level accuracy gives access to
small spectral differences among the different species and, in turn, this
allows scrutinizing the universality of CR acceleration, which is expected in
the standard scenario of CR shock acceleration. While pre-AMS-02 data already
indicated a violation of the universality between protons and helium, it is
still an open question if at least helium and heavier nuclei can be reconciled.
To address this issue, we performed a joint analysis using the AMS-02 CR
measurements of antiprotons, protons, helium, helium 3, boron, carbon,
nitrogen, and oxygen. We explore two competing propagation scenarios, one with
a break in the diffusion coefficient at a few GVs and no reacceleration, and
another one with reacceleration and with a break in the injection spectra of
primaries. Furthermore, we explicitly consider the impact of the uncertainties
in the nuclear production cross-sections of secondaries by including nuisance
parameters in the fit. The resulting parameter space is explored with the help
of Monte Carlo methods. We find that, contrary to the naive expectation, in the
standard propagation scenarios CR universality is violated also for He, on the
one hand, and C, N, and O, on the other hand, i.e., different injection slopes
(at the level of ) are required to explain the observed
spectra. As an alternative, we explore further propagation scenarios, inspired
by non-homogeneous diffusion, which might save universality. Finally, we also
investigate the universality of CR propagation, i.e., we compare the
propagation properties inferred using only light nuclei (, p, He,
He) with the ones inferred using only heavier nuclei (B, C, N, O).Comment: 25 pages, 9 figures; v2: results and conclusion unchanged; expanded
introduction and discussion; matches accepted version by PR
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