arXiv subjects

Ina Sarcevic

Publications and source records attributed to Ina Sarcevic.

At least 37 records · Page 2Linked to original sources

arXiv2016

Prompt atmospheric neutrino fluxes: perturbative QCD models and nuclear effects

We evaluate the prompt atmospheric neutrino flux at high energies using three different frameworks for calculating the heavy quark production cross section in QCD: NLO perturbative QCD, $k_T$ factorization including low-$x$ resummation, and the dipole model including parton saturation. We use QCD parameters, the value for the charm quark mass and the range for the factorization and renormalization scales that provide the best description of the total charm cross section measured at fixed target experiments, at RHIC and at LHC. Using these parameters we calculate differential cross sections for charm and bottom production and compare with the latest data on forward charm meson production from LHCb at $7$ TeV and at $13$ TeV, finding good agreement with the data. In addition, we investigate the role of nuclear shadowing by including nuclear parton distribution functions (PDF) for the target air nucleus using two different nuclear PDF schemes. Depending on the scheme used, we find the reduction of the flux due to nuclear effects varies from $10\%$ to $50 \%$ at the highest energies. Finally, we compare our results with the IceCube limit on the prompt neutrino flux, which is already providing valuable information about some of the QCD models.

hep-ph↗

arXiv2015

Perturbative charm production and the prompt atmospheric neutrino flux in light of RHIC and LHC

We re-evaluate the prompt atmospheric neutrino flux, using the measured charm cross sections at RHIC and the Large Hadron Collider to constrain perturbative QCD parameters such as the factorization and renormalization scales, as well as modern parton distribution functions and recent estimates of the cosmic-ray spectra. We find that our result for the prompt neutrino flux is lower than previous perturbative QCD estimates and, consequently, alters the signal-to-background statistics of the recent IceCube measurements at high energies.

hep-ph↗

arXiv2014

Charm decay in slow-jet supernovae as the origin of the IceCube ultra-high energy neutrino events

We investigate whether the recent ultra-high energy (UHE) neutrino events detected at the IceCube neutrino observatory could come from the decay of charmed mesons produced within the mildly relativistic jets of supernova-like astrophysical sources. We demonstrate that the $5.7σ$ excess of neutrinos observed by IceCube in the energy range 30 TeV--2 PeV can be explained by a diffuse flux of neutrinos produced in such slow-jet supernovae, using the values of astrophysical and QCD parameters within the theoretical uncertainties associated with neutrino production from charmed meson decay in astrophysical sources. We discuss the theoretical uncertainties inherent in the evaluation of charm production in high energy hadronic collisions, as well as the astrophysical uncertainties associated with slow-jet supernova sources. The proton flux within the source, and therefore also the produced neutrino flux, is cut off at around a few PeV, when proton cooling processes become dominant over proton acceleration. This directly explains the sudden drop in event rates at energies above a few PeV. We incorporate the effect of energy dependence in the spectrum-weighted charm production cross-section and show that this has a very significant effect on the shape, magnitude and cut-off energies for the neutrino flux.

astro-ph.HE↗

arXiv2014

Reconciling neutrino flux from heavy dark matter decay and recent events at IceCube

The IceCube detector has recently reported the observation of 28 events at previously unexplored energies. While the statistics of the observed events are still low, these events hint at the existence of a neutrino flux over and above the atmospheric neutrino background. We investigate the possibility that a significant component of the additional neutrino flux originates due to the decay of a very heavy dark matter (VHDM) particle via several possible channels into standard model particles. We show that a combination of a power law astrophysical neutrino spectrum and the neutrino flux from the decay of a DM species of mass in the range $150-400$ TeV improves the fit to the observed neutrino events than that obtained from a best-fit astrophysical flux alone. Assuming the existence of an astrophysical background described by the IC best-fit, we also show that, for the decay of even heavier DM particles ($m_{\text{DM}} \sim 1$ PeV), the same observations impose significant constraints on the decay lifetimes. Allowing the astrophysical flux normalization to vary leads to modifications of these limits, however, there is still a range of dark matter mass and lifetime that is excluded by the IC results.

hep-ph↗

arXiv2014

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 $~10^3$ GeV/cm$^3$ and dark matter mass $m_χ$ 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 $m_χ\sim 10$ GeV when the dark matter interaction cross section with the nucleons ranges from $σ_{χn}\sim 10^{-52}$ cm$^2$ to $10^{-57}$ cm$^2$, the dark matter self-interaction cross section limit is $σ_{χχ}< 10^{-33}$ cm$^2$, which is about ten orders of magnitude stronger than the Bullet Cluster limit.

hep-ph↗

arXiv2011

Radio Cherenkov signals from the Moon: neutrinos and cosmic rays

Neutrino production of radio Cherenkov signals in the Moon is the object of radio telescope observations. Depending on the energy range and detection parameters, the dominant contribution to the neutrino signal may come from interactions of the neutrino on the Moon facing the telescope, rather than neutrinos that have traversed a portion of the Moon. Using the approximate analytic expression of the effective lunar aperture from a recent paper by Gayley, Mutel and Jaeger, we evaluate the background from cosmic ray interactions in the lunar regolith. We also consider the modifications to the effective lunar aperture from generic non-standard model neutrino interactions. A background to neutrino signals are radio Cherenkov signals from cosmic ray interactions. For cosmogenic neutrino fluxes, neutrino signals will be difficult to observe because of low neutrino flux at the high energy end and large cosmic ray background in the lower energy range considered here. We show that lunar radio detection of neutrino interactions is best suited to constrain or measure neutrinos from astrophysical sources and probe non-standard neutrino-nucleon interactions such as microscopic black hole production.

astro-ph.CO↗

arXiv2011

The AdS Graviton/Pomeron Description of Deep Inelastic Scattering at Small x

In the holographic or AdS/CFT dual to QCD, the Pomeron is identified with a Reggeized Graviton in $AdS_5$. We emphasize the importance of confinement, which in this context corresponds to a deformation of $AdS_5$ geometry in the IR. The holographic Pomeron provides a very good fit to the combined data from HERA for Deep Inelastic Scattering at small $x$, lending new confidence to this AdS dual approach to high energy diffractive scattering.

hep-ph↗

arXiv2010

Probing dark matter models with neutrinos from the Galactic center

We calculate the contained and upward muon and shower fluxes due to neutrinos produced via dark matter annihilation or decay in the Galactic center. We consider dark matter models in which the dark matter particle is a gravitino, a Kaluza-Klein particle and a particle in leptophilic models. The Navarro-Frenk-White profile for the dark matter density distribution in the Galaxy is used. We incorporate neutrino oscillations by assuming maximal mixing and parametrize our results for muon and shower distributions. The muon and shower event rates and the minimum observation times in order to reach 2$σ$ detection significance are evaluated. We illustrate how observation times vary with the cone half angle chosen about the Galactic center, with the result that the optimum angles are about 10$^\circ$ and 50$^\circ$ for the muon events and shower events, respectively. We find that for the annihilating dark matter models such as the leptophilic and Kaluza-Klein models, upward and contained muon as well as showers are 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. We also illustrate for each model the parameter space probed with the 2$σ$ signal detection in five years. We discuss how the shape of the parameter space probed change with significance and the observation time.

hep-ph↗

arXiv2010

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 $150 {\rm GeV} <m_χ< 1$ TeV for $E_{sh}^{th} = 100$ GeV.

hep-ph↗

arXiv2009

Muon Fluxes From Dark Matter Annihilation

We calculate the muon flux from annihilation of the dark matter in the core of the Sun, in the core of the Earth and from cosmic diffuse neutrinos produced in dark matter annihilation in the halos. We consider model-independent direct neutrino production and secondary neutrino production from the decay of taus produced in the annihilation of dark matter. We illustrate how muon energy distribution from dark matter annihilation has a very different shape than muon flux from atmospheric neutrinos. 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 contrast our results to the ones previously obtained in the literature, illustrating the importance of properly treating muon propagation and energy loss. We comment on neutrino flavor dependence and their detection.

hep-ph↗

arXiv2009

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 $p_T^H > 100$ GeV, when $M_P=1$TeV. Diphotons from Higgs, when Higgs is produced from evaporation of black holes, are dominant over the standard model prediction, for diphoton rapidity $|y_{γγ}| \leq 1$, while bottom quarks are dominant over QCD background for large bottom quark transverse momentum, $p_T^b > 300$ GeV, when $M_P=1$ 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.

hep-ph↗

arXiv2009

High energy neutrinos from charm in astrophysical sources

Charm production gives rise to a flux of very high energy neutrinos from astrophysical sources with jets driven by central engines, such as gamma ray bursts or supernovae with jets. The neutrino flux from semi-leptonic decays of charmed mesons is subject to much less hadronic and radiative cooling than the conventional flux from pion and kaon decays and therefore has a dominant contribution at higher energies, of relevance to future ultrahigh energy neutrino experiments.

astro-ph↗

arXiv2008

Prompt neutrino fluxes from atmospheric charm

We calculate the prompt neutrino flux from atmospheric charm production by cosmic rays, using the dipole picture in a perturbative QCD framework, which incorporates the parton saturation effects present at high energies. We compare our results with the next-to-leading order perturbative QCD result and find that saturation effects are large for neutrino energies above 10^6 GeV, leading to a substantial suppression of the prompt neutrino flux. We comment on the range of prompt neutrino fluxes due to theoretical uncertainties.

hep-ph↗

arXiv2007

Probing Late Neutrino Mass Properties with Supernova Neutrinos

Models of late-time neutrino mass generation contain new interactions of the cosmic background neutrinos with supernova relic neutrinos (SRNs) through exchange of the on-shell light boson, leading to significant modification of the differential SRN flux observed at earth. We consider Abelian U(1) model for generating neutrino masses at low scales and we show that there is a large parameter space in this model for which the changes induced in the flux by the exchange of the light bosons might allow one to distinguish between neutrinos being Majorana or Dirac particles, the type of neutrino mass hierarchy (normal or inverted or quasi-degenerate), and could also possibly determine the absolute values of the neutrino masses. Measurements of the presence of these effects would be possible at the next-generation water Cerenkov detectors enriched with Gadolinium, or a large 100 kton liquid argon detector.

hep-ph↗

arXiv2006

Mini Z' Burst from Relic Supernova Neutrinos and Late Neutrino Masses

In models in which neutrinos are light, due to a low scale of symmetry breaking, additional light bosons are generically present. We show that the interaction between diffuse relic supernova neutrinos (RSN) and the cosmic background neutrinos, via exchange of these light scalars, can result in a dramatic change of the supernova (SN) neutrinos flux. Measurement of this effect with current or future experiments can provide a spectacular direct evidence for the low scale models. We demonstrate how the observation of neutrinos from SN1987A constrains the symmetry breaking scale of the above models. We also discuss how current and future experiments may confirm or further constrain the above models, either by detecting the ``accumulative resonance'' that diffuse RSN go through or via a large suppression of the flux of neutrinos from nearby < O(Mpc) SN bursts.

hep-ph↗

arXiv2003

Ultrahigh Energy Neutrinos

The ultrahigh energy neutrino cross section is well understood in the standard model for neutrino energies up to 10$^{12}$ GeV. Test of neutrino oscillations ($ν_μ\leftrightarrowν_τ$) from extragalactic sources of neutrinos are possible with large underground detectors. Measurments of horizontal air shower event rates at neutrino energies above 10$^{10}$ GeV will be able to constrain nonstandard model contributions to the neutrino-nucleon cross section, e.g., from mini-black hole production.

hep-ph↗

arXiv2003

Hadrons as Signature of Black Hole Production at the LHC

In models with several large extra dimensions and fundamental Planck scale of the order of 1 TeV, black holes can be produced in large numbers at LHC energies. We compute the charged hadron spectra obtained from the decay of black holes created in p-p and Pb+Pb collisions at LHC. We show that hadrons from black hole decay dominate at transverse momenta p_T>30-100 GeV/c compared to usual QCD processes and black hole production signals are easy to identify in hadron transverse momentum spectra. Furthermore we show that a measurement of the charged hadron spectra probes Planck scales up to ~5 TeV for any number of extra dimensions.

hep-ph↗

arXiv2002

On Black Hole Detection with the OWL/Airwatch Telescope

In scenarios with large extra dimensions and TeV scale gravity ultrahigh energy neutrinos produce black holes in their interactions with the nucleons. We show that ICECUBE and OWL may observe large number of black hole events and provide valuable information about the fundamental Planck scale and the number of extra dimensions. OWL is especially well suited to observe black hole events produced by neutrinos from the interactions of cosmic rays with the 3 K background radiation. Depending on the parameters of the scenario of large extra dimensions and on the flux model, as many as 28 events per year are expected for a Planck scale of 3 TeV.

hep-ph↗