8 research outputs found
Muon Fluxes and Showers from Dark Matter Annihilation in the Galactic Center
We calculate contained and upward muon flux and contained shower event rates
from neutrino interactions, when neutrinos are produced from annihilation of
the dark matter in the Galactic Center. We consider model-independent direct
neutrino production and secondary neutrino production from the decay of taus, W
bosons and bottom quarks produced in the annihilation of dark matter. We
illustrate how muon flux from dark matter annihilation has a very different
shape than the muon flux from atmospheric neutrinos. We also discuss the
dependence of the muon fluxes on the dark matter density profile and on the
dark matter mass and of the total muon rates on the detector threshold. We
consider both the upward muon flux, when muons are created in the rock below
the detector, and the contained flux when muons are created in the (ice)
detector. We also calculate the event rates for showers from neutrino
interactions in the detector and show that the signal dominates over the
background for TeV for GeV.Comment: 13 pages, 14 figures, 3 tables; Fig. 14 replaced and references
added; new table and references added, discussion extended, version accepted
for publication in Phys Rev
Higgs Production and Decay from TeV Scale Black Holes at the LHC
We perform detailed study of the Higgs production and decay, when Higgs is
emitted from the black holes produced in proton-proton collisions at the Large
Hadron Collider. We show that black hole production can significantly enhance
the signal for the Higgs search at the LHC. We evaluate rapidity distribution
of diphotons and transverse momentum distribution of bottom quarks, photons,
tau leptons, top quarks and W bosons from Higgs decay, when Higgs is emitted
from the black hole and also in case when these particles are produced directly
from the black hole evaporation. We compare our results with the standard model
backgrounds. We find that Higgs production from black holes is dominant over
standard model production for GeV, when TeV. Diphotons
from Higgs, when Higgs is produced from evaporation of black holes, are
dominant over the standard model prediction, for diphoton rapidity , while bottom quarks are dominant over QCD background for
large bottom quark transverse momentum, GeV, when TeV. We
show that measurements of the photon and bottom quark transverse momentum
distribution can provide valuable information about the value of the
fundamental Planck scale. We also propose a new signal for black hole
production at the LHC, an onset of increasing transverse momentum distribution
of bottom quarks with large transverse momentum.Comment: 28 pages, 10 figures, 2 tables. Typo corrected; version accepted for
publication in Phys. Rev.
On the capture of dark matter by neutron stars
We calculate the number of dark matter particles that a neutron star
accumulates over its lifetime as it rotates around the center of a galaxy, when
the dark matter particle is a self-interacting boson but does not
self-annihilate. We take into account dark matter interactions with baryonic
matter and the time evolution of the dark matter sphere as it collapses within
the neutron star. We show that dark matter self-interactions play an important
role in the rapid accumulation of dark matter in the core of the neutron star.
We consider the possibility of determining an exclusion region of the parameter
space for dark matter mass and dark matter interaction cross sections based on
the observation of old neutron stars with strong dark matter self-interactions.
We show that for a dark matter density of GeV/cm and dark matter
mass less than approximately 10 GeV, there is a potential exclusion
region for dark matter interactions with nucleons that is three orders of
magnitude more stringent than without self-interactions. The potential
exclusion region for dark matter self-interaction cross sections is many orders
of magnitude stronger than the current Bullet Cluster limit. For example, for
high dark matter density regions, we find that for GeV when the
dark matter interaction cross section with the nucleons ranges from
cm to cm, the dark matter
self-interaction cross section limit is cm,
which is about ten orders of magnitude stronger than the Bullet Cluster limit.Comment: 12 pages, 9 figures, v2. change in treatment of dark matter collapse
in neutron star, conclusions changed; v3. minor revisions of text for
clarification, added references, v4. version accepted for publication in JCA
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Neutrino Signals from Dark Matter
Large-scale neutrino telescopes will be powerful tools to observe multitude of mysterious phenomena happening in the Universe. The dark matter puzzle is listed as one of them. In this study, indirect detection of dark matter via neutrino signals is presented. The upward muon, the contained muon and the hadronic shower fluxes are calculated, assuming annihilation/decay of the dark matter in the core of the astrophysical objects and in the Galactic center. Direct neutrino production and secondary neutrino production from the decay of Standard Model particles produced in the annihilation/decay of dark matter are studied. The results are contrasted to the ones previously obtained in the literature, illustrating the importance of properly treating muon propagation and energy loss for the upward muon flux. The dependence of the dark matter signals on the density profile, the dark matter mass and the detector threshold are discussed. Different dark matter models (gravitino, Kaluza-Klein and leptophilic) which can account for recent observations of some indirect searches are analyzed regarding their detection in the kilometer size neutrino detectors in the near future. Muon and shower rates and the minimum observation times in order to reach 2σ detection significance are evaluated, with the result suggesting that the optimum cone half angles chosen about the Galactic center are about 10° (50°) for the muon (shower) events. A detailed analysis shows that for the annihilating dark matter models such as the leptophilic and Kaluza-Klein models, upward and contained muon as well as showers yield promising signals for dark matter detection in just a few years of observation, whereas for decaying dark matter models, the same observation times can only be reached with showers. The analytical results for the final fluxes are also obtained as well as parametric forms for the muon and shower fluxes for the dark matter models considered in this study
Neutrino signals from dark matter
Large-scale neutrino telescopes will be powerful tools to observe multitude of mysterious phenomena happening in the Universe. The dark matter puzzle is listed as one of them. In this study, indirect detection of dark matter via neutrino signals is presented. The upward muon, the contained muon and the hadronic shower fluxes are calculated, assuming annihilation/decay of the dark matter in the core of the astrophysical objects and in the Galactic center. Direct neutrino production and secondary neutrino production from the decay of Standard Model particles produced in the annihilation/decay of dark matter are studied. The results are contrasted to the ones previously obtained in the literature, illustrating the importance of properly treating muon propagation and energy loss for the upward muon flux. The dependence of the dark matter signals on the density profile, the dark matter mass and the detector threshold are discussed. Different dark matter models (gravitino, Kaluza-Klein and leptophilic) which can account for recent observations of some indirect searches are analyzed regarding their detection in the kilometer size neutrino detectors in the near future. Muon and shower rates and the minimum observation times in order to reach 2σ detection significance are evaluated, with the result suggesting that the optimum cone half angles chosen about the Galactic center are about 10° (50°) for the muon (shower) events. A detailed analysis shows that for the annihilating dark matter models such as the leptophilic and Kaluza-Klein models, upward and contained muon as well as showers yield promising signals for dark matter detection in just a few years of observation, whereas for decaying dark matter models, the same observation times can only be reached with showers. The analytical results for the final fluxes are also obtained as well as parametric forms for the muon and shower fluxes for the dark matter models considered in this study
Kırmızı gürültü güç yoğunluğu belirleme teknikleri ve sax j2103.5+4545 kaynağına uygulaması
In this thesis,red noise analysis techniques are presented. The necessity of the use of the window functions and the Deeter polynomial method in order to determine red noise is discussed. The method was applied to the source SAX J2103.5+4545 which showed a white torque noise with a relatively low noise strength due to its being a transient system.M.S. - Master of Scienc