197490011
Constraints on the dark matter annihilation scenario of Fermi 130 GeV $\gamma$-ray line emission by continuous gamma-rays, Milky Way halo, galaxy clusters and dwarf galaxies observations
It was recently reported that there may exist monochromatic $\gamma$-ray emission at $\sim 130$ GeV from the Galactic center in the Fermi Large Area Telescope data, which might be related with dark matter (DM) annihilation. In this work we carry out a comprehensive check of consistency of the results with the DM annihilation scenario, using the 3.7 yrs Fermi observation of the inner Galaxy, Galactic halo, clusters of galaxies and dwarf galaxies. The results found are as follows. 1) Very strong constraints on the DM annihilation into continuous $\gamma$-rays from the Galactic center are set, which are as stringent as the "natural" scale assuming thermal freeze-out of DM. Such limit sets strong constraint on the DM models to explain the line emission. 2) No line emission from the Galactic halo is found in the Fermi data, and the constraints on line emission is marginally consistent with the DM annihilation interpretation of the $\sim 130$ GeV line emission from the inner Galaxy. 3) No line emission from galaxy clusters and dwarf galaxies is detected, although possible concentration of photons from clusters in 120-140 GeV is revealed. The constraints from clusters and dwarf galaxies are weak and consistent with the DM annihilation scenario to explain the $\sim 130$ GeV line emission.
118657682
New constraints on primordial minihalo abundance using cosmic microwave background observations
It was proposed that the massive compact halo objects (MCHOs) would be produced during an earlier epoch of cosmology if the density perturbations are between $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ and 0.3. Then these objects can accrete dark matter particles onto them due to their high density. If the dark matter is in the form of the weakly interacting massive particles, the MCHOs can have a significant effect on the evolution of cosmology due to the dark matter annihilation within them. Using the WMAP-7 years data, we investigated the constraints on the current abundance of MCHOs (${f}_{\mathrm{MCHOs}}$) formed during the ${e}^{+}{e}^{\ensuremath{-}}$ annihilation phase transition. We have found that the $2\ensuremath{\sigma}$ constraint is ${f}_{\mathrm{MCHOs}}\ensuremath{\lesssim}{10}^{\ensuremath{-}4}$ for dark matter masses in the range between 1 GeV and 1 TeV.
118532372
Constraints on ultracompact minihalos from extragalactic {\gamma}-ray background
It has been proposed that ultracompact minihalos (UCMHs) might be formed in earlier epoch. If dark matter consists of Weakly Interacting Massive Particles (WIMPs), UCMHs can be treated as the γ-ray sources due to dark matter annihilation within them. In this paper, we investigate the contributions of UCMHs formed during three phase transitions (i.e., electroweak symmetry breaking, QCD confinement and e+e− annihilation) to the extragalactic γ-ray background. Moreover, we use the Fermi-LAT observation data of the extragalactic γ-ray background to get the constraints on the current abundance of UCMHs produced during these phase transitions. We also compare these results with those obtained from Cosmic Microwave Background (CMB) observations and find that the constraints from the Fermi-LAT are more stringent than those from CMB.
119290233
Fermi LAT search for internal bremsstrahlung signatures from dark matter annihilation
A commonly encountered obstacle in indirect searches for galactic dark matter is how to disentangle possible signals from astrophysical backgrounds. Given that such signals are most likely subdominant, the search for pronounced spectral features plays a key role for indirect detection experiments; monochromatic gamma-ray lines or similar features related to internal bremsstrahlung, in particular, provide smoking gun signatures. We perform a dedicated search for the latter in the data taken by the Fermi gamma-ray space telescope during its first 43 months. To this end, we use a new adaptive procedure to select optimal target regions that takes into account both standard and contracted dark matter profiles. The behaviour of our statistical method is tested by a subsampling analysis of the full sky data and found to reproduce the theoretical expectations very well. The limits on the dark matter annihilation cross-section that we derive are stronger than what can be obtained from the observation of dwarf galaxies and, at least for the model considered here, collider searches. While these limits are still not quite strong enough to probe annihilation rates expected for thermally produced dark matter, future prospects to do so are very good. In fact, we already find a weak indication, with a significance of 3.1σ (4.3σ) when (not) taking into account the look-elsewhere effect, for an internal bremsstrahlung-like signal that would correspond to a dark matter mass of ~150 GeV; the same signal is also well fitted by a gamma-ray line at around 130 GeV. Although this would be a fascinating possibility, we caution that a much more dedicated analysis and additional data will be necessary to rule out or confirm this option.
117724442
Galaxy Clusters and Gamma-Ray Lines: Probing Gravitino Dark Matter with the Fermi LAT
If dark matter particles are not perfectly stable, their decay products might be seen in the cosmic-ray fluxes. A natural candidate for decaying dark matter is the gravitino in R-parity violating scenarios. In the relevant GeV-TeV energy range, the Fermi Large Area Telescope (LAT) is now measuring cosmic gamma-ray fluxes with an unprecedented precision. We use the Fermi LAT gamma-ray data to search for signatures from gravitino dark matter particles, concentrating on gamma-ray lines and galaxy cluster observations. Implications of our results for the decay length of the next-to-lightest superparticle, which could be seen at the LHC in the near future, are discussed.
383345
Probing dark matter decay and annihilation with Fermi LAT observations of nearby galaxy clusters
Galaxy clusters are promising targets for indirect dark matter searches. Gamma-ray signatures from the decay or annihilation of dark matter particles inside these clusters could be observable with the Fermi Large Area Telescope (LAT). Based on three years of Fermi LAT gamma-ray data, we analyze the flux coming from eight nearby clusters individually as well as in a combined likelihood analysis. Concentrating mostly on signals from dark matter decay, we take into account uncertainties of the cluster masses as determined by X-ray observations and model the cluster emission as extended sources. Searching for different hadronic and leptonic decay and annihilation spectra, we do not find significant emission from any of the considered clusters and present limits on the dark matter lifetime and annihilation cross-section. We compare our lifetime limits derived from cluster observations with the limits that can be obtained from the extragalactic gamma-ray background (EGBG), and find that in case of hadronic decay the cluster limits become competitive at dark matter masses below a few hundred GeV. In case of leptonic decay, however, galaxy cluster limits are stronger than the limits from the EGBG over the full considered mass range. Finally, we show that in presence of dark matter substructures down to 10?6 solar masses the limits on the dark matter annihilation cross-section could improve by a factor of a few hundred, possibly going down to the thermal cross-section of 3 ? 10?26cm3s?1 for dark matter masses 150GeV and annihilation into b. As a direct application of our results, we derive limits on the lifetime of gravitino dark matter in scenarios with R-parity violation. Implications of these limits for the possible observation of long-lived superparticles at the LHC are discussed.
119248497
Strange quark matter in strong magnetic fields within a confining model
model. The confinement is modeled by means of the Richardson potential for quark-quark interaction modified suitably to account for a strong magnetic field. We compare our results for the equation of state and magnetization of matter to those derived within the MIT bag model. The differences between these models arise mainly due to the momentum dependence of the strong interaction between quarks in the Richardson model. Specifically, we find that the magnetization of strange quark matter in this model �
11909349
Simulation of ultra-short pulses in a storage ring
Simulation study was performed with the tracking code Elegant [M. Borland, APS Report LS-287] to show beam quality evolution for a short, intense electron bunch after being injected to the SPEAR3 storage ring. The electron bunch with an intensity of 1 mA (0.78 nC) and a length of nearly 1 ps (FWHM) is found to degrade rapidly due to coherent synchrotron radiation (CSR) which causes large uneven longitudinal phase space distortion. The bunch length remains short and the longitudinal line density remains smooth for about 10 turns. For such a beam to circulate in the ring, a total of 10 MV rf power is needed to compensate for the energy loss.
16264551
Neutrino Emission From Inhomogeneous Pion Condensed Quark Matter
It is believed that quark matter can exist in neutron star interior if the baryon density is high enough. When there is a large isospin density, quark matter could be in a pion condensed phase. We compute neutrino emission from direct Urca processes in such a phase, particularly in the inhomogeneous Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) states. The neutrino emissivity and specific heat are obtained, from which the cooling rate is estimated.
18932536
Bunch length measurements in SPEAR3
A series of bunch length measurements were made in SPEAR3 for two different machine optics. In the achromatic optics the bunch length increases from the low-current value of 16.6 ps rms to about 30 ps at 25 ma/bunch yielding an inductive impedance of -0.17 Omega. Reducing the momentum compaction factor by a factor of ~60 [1] yields a low-current bunch length of ~4 ps rms. In this paper we review the experimental setup and results.
118564801
BCS-BEC crossover and thermodynamics in asymmetric nuclear matter with pairings in isospin I=0 and I=1 channels
The Bardeen/Cooper/Schrieffer-Bose-Einstein condensation (BCS-BEC) crossover and phase diagram for asymmetric nuclear superfluid with pairings in isospin I = 0 and I = 1 channels are investigated at the mean-field level by using a density-dependent nucleon-nucleon potential. Induced by the in-medium nucleon mass and density-dependent coupling constants, neutron-proton Cooper pairs could be in BEC state at sufficiently low density, but there is no chance for the BEC formation of neutron-neutron and proton-proton pairs at any density and asymmetry. We calculate the phase diagram in asymmetry-temperature plane for weakly interacting nuclear superfluid and find that including the I = 1 channel changes significantly the phase structure at low temperature. There appears a new phase with both I = 0 and I = 1 pairings at low temperature and low asymmetry, and the gapless state in any phase with I = 1 pairing is washed out and all excited nucleons are fully gapped.