arXiv subjects
Publications and source records attributed to I. Sarcevic.
This is the report for the topical group Theory of Neutrino Physics (TF11/NF08) for Snowmass 2021. This report summarizes the progress in the field of theoretical neutrino physics in the past decade, the current status of the field, and the prospects for the upcoming decade.
We study the signal for the detection of quasi-stable supersymmetric particles produced in interactions of cosmogenic neutrinos. We consider energy loss of high energy staus due to photonuclear and weak interactions. We show that there are optimal nadir angles for which the stau signal is a factor of several hundred larager than muons. We discuss how one could potentially eliminate the muon background by considering the energy loss of muons in the detector. We also show results for the showers produced by weak interactions of staus that reach the detector.
Neutrino telescopes may have the potential to detect the quasi-stable staus predicted by supersymmetric models. Detection depends on stau electromagnetic energy loss and weak interactions. We present results for the weak interaction contribution to the energy loss of high energy staus as they pass through rock. We show that the neutral current weak interaction contribution to the energy loss increases with energy, but it is much smaller than the photonuclear energy loss, however, the charged current contribution may become the dominant process above the energy of $\sim 10^9$ GeV, depending on the parameters of the model. As a consequence, the stau range may be reduced above $\sim 10^9$ GeV as compared to the range neglecting weak interactions. We contrast this with the tau range which is barely changed with the inclusion of charged current interactions.
We discuss the interplay between electromagnetic energy loss and weak interactions in the context of quasistable particle particle propagation through materials. As specific examples, we consider staus, where weak interactions may play a role, and taus, where they don't.
We study ultrahigh energy astrophysical neutrinos and their interactions within the Standard Model and beyond. We consider propagation of muon neutrinos, tau neutrinos that originate in $ν_μ\to ν_τ$ oscillations, and tau leptons produced in charged-current neutrino interactions. We show that high energy taus lose their energy through bremsstrahlung, pair production and photonuclear processes until they reach energy of $\sim 10^8$ GeV, bellow which they are more likely to decay. Neutrino interactions at energies above $10^8$GeV could lead to the production of microscopic black holes predicted in theories of extra dimensions, or they can undergo instanton-induced processes. We discuss potential signals for these processes in detectors such as IceCube and ANITA.
The potential for neutrino telescopes to discover charged stau production in neutrino-nucleon interactions in Earth depends in part on the stau lifetime and range. In some supersymmetric scenarios, the next lightest supersymmetric particle is a stau with a decay length on the scale of 10 km. We evaluate the electromagnetic energy loss as a function of energy and stau mass. The energy loss parameter $β$ scales as the inverse stau mass for the dominating electromagnetic processes, photonuclear and $e^+e^-$ pair production. The range can be parameterized as a function of stau mass, initial energy and minimum final energy. In comparison to earlier estimates of the stau range, our results are as much as a factor of two larger, improving the potential for stau discovery in neutrino telescopes.
Astrophysical sources of ultrahigh energy neutrinos yield tau neutrino fluxes due to neutrino oscillations. We study in detail the contribution of tau neutrinos with energies above $10^6$ GeV relative to the contribution of the other flavors. We consider several different initial neutrino fluxes and include tau neutrino regeneration in transit through the Earth and energy loss of charged leptons. We discuss signals of tau neutrinos in detectors such as IceCube, RICE and ANITA.
Various pion and photon production mechanisms in high-energy nuclear collisions at RHIC and LHC are discussed. Comparison with RHIC data is done whenever possible. The prospect of using electromagnetic probes to characterize quark-gluon plasma formation is assessed.
Astrophysical sources of ultrahigh energy neutrinos yield tau neutrino fluxes due to neutrino oscillations. We study in detail the contribution of tau neutrinos with energies above PeV relative to the contribution of the other flavors. We consider several different initial neutrino fluxes and include tau neutrino regeneration in transit through the Earth and energy loss of charged leptons. We discuss signals of tau neutrinos in detectors such as IceCube, RICE and ANITA.
Astrophysical sources of ultrahigh energy neutrinos yield tau neutrino fluxes due to neutrino oscillations. At neutrino energies in the EeV range, radio Cherenkov detection methods show promise for detecting these fluxes. We quantify the tau neutrino contributions to the signal in, for example, a detector like the Radio Ice Cherenkov Experiment (RICE) for a Z-burst flux prediction. Tau neutrino regeneration in transit through the Earth, including energy loss, is evaluated.
We present results for the large-$p_T$ inclusive $π^0$ production in p-p and A-A collisions at RHIC and LHC energies. We include the full next-to-leading order radiative corrections, $O(α_s^3)$, and nuclear effects such as parton energy loss and nuclear shadowing. We find the next-to-leading order corrections and the parton energy loss effect to be large and $p_T$ dependent, while the nuclear shadowing effects are small ($< 10%$). We calculate the ratio of prompt photons to neutral pions produced in heavy ion collisions and show that at RHIC energies this ratio increases with $p_T$ approaching one at $p_T \sim 8$ GeV, due to the large suppression of $π^0$ production. We show that at the LHC, this ratio has a steep $p_T$ dependence and approaches 25% effect at $p_T \sim 40$ GeV. We discuss theoretical uncertainties inherent in our calculation, such as choice of the renormalization, factorization and fragmentation scales and the K-factors which signify the size of higher-order corrections.
We present results for inclusive $π^0$ production in proton-proton and in Au-Au at RHIC energy $\sqrt s=200$ GeV. We use next-to-leading order perturbative QCD calculation and we include nuclear effects such as parton energy loss and nuclear shadowing. We consider the ratio of $π^0$ distribution in Au-Au and p-p collisions for $p_T > 3$ GeV for three cases of parton energy loss: 1) constant parton energy loss per parton scattering, $ε^a_n=const$, 2) Landau-Pomeranchuk-Migdal energy-dependent energy loss, $ε^a_n \sim \sqrt E^a_n$ and 3) Bethe-Heitler energy-dependent energy loss, $ε^a_n \sim E^a_n$. We show that recently observed suppression of $π^0$ production in Au-Au collisions at RHIC, which is found to increase with $p_T$ increasing from 3GeV to 8GeV, can be reproduced by $ε^a_n=0.06 E^a_n$. We show that the ratio of prompt photons to neutral pions produced in Au-Au collisions at RHIC has a strong $p_T$ dependence approaching one at $p_T\sim 10$GeV.
We present results for prompt photon and inclusive $π^0$ production in p-p and A-A collisions at RHIC and LHC energies. We include the full next-to-leading order radiative corrections and nuclear effects, such as nuclear shadowing and parton energy loss. We find the next-to-leading order corrections to be large and $p_T$ dependent. We show how measurements of $π^0$ production at RHIC and LHC, at large $p_T$, can provide valuable information about the nature of parton energy loss. We calculate the ratio of prompt photons to neutral pions and show that at RHIC energies this ratio increases with $p_T$ approaching one at $p_T \sim 10$ GeV, due to the large suppression of $π^0$ production. We show that at the LHC, this ratio has steep $p_T$ dependence and approaches 10% effect at $p_T \sim 20$ GeV.
The energy dependence of "secondary" neutrinos from the process nutau->tau->numubar->mubar for two input tau neutrino fluxes (F^0_nu ~ 1/E_nu and 1/E_nu^2), assumed to have been produced via neutrino oscillations from extragalactic sources, is evaluated to assess the impact of secondary neutrinos on the upward muon rates in a km^3 detector. We show that the secondard fluxes are considerably suppressed for the steeper flux, and even for fluxes ~ 1/E_nu, the secondary flux will be difficult to observe experimentally.
In this summary of the considerations of the QCD working group at Snowmass 2001, the roles of quantum chromodynamics in the Standard Model and in the search for new physics are reviewed, with empahsis on frontier areas in the field. We discuss the importance of, and prospects for, precision QCD in perturbative and lattice calculations. We describe new ideas in the analysis of parton distribution functions and jet structure, and review progress in small-$x$ and in polarization.
The ultrahigh energy cross section for neutrino interactions with nucleons is reviewed, and unitarity constraints are discussed. We argue that existing QCD extrapolations are self-consistent, and do not imply a breakdown of the perturbative expansion in the weak coupling.
The photonuclear contribution to charged lepton energy loss has been re-evaluated taking into account HERA results on real and virtual photon interactions with nucleons. With large $Q^2$ processes incorporated, the average muon range in rock for muon energies of $10^9$ GeV is reduced by only 5% as compared with the standard treatment. We have calculated the tau energy loss for energies up to $10^9$ GeV taking into consideration the decay of the tau. A Monte Carlo evaluation of tau survival probability and range show that at energies below $10^7-10^8$ GeV, depending on the material, only tau decays are important. At higher energies the tau energy losses are significant, reducing the survival probability of the tau. We show that the average range for tau is shorter than its decay length and reduce to 17 km in water for an incident tau energy of $10^9$ GeV, as compared with its decay length of 49 km at that energy. In iron, the average tau range is 4.7 km for the same incident energy.
We calculate the inclusive cross section for prompt photon production in heavy-ion collisions at RHIC energies ($\sqrt{s}=130$ GeV and $\sqrt{s}=200$ GeV) in the central rapidity region including next-to-leading order, $O(α_{em}α_s^2)$, radiative corrections, initial state nuclear shadowing and parton energy loss effects. We show that there is a significant suppression of the nuclear cross section, up to $\sim 30%$ at $\sqrt{s}=200$ GeV, due to shadowing and medium induced parton energy loss effects. We find that the next-to-leading order contributions are large and have a strong $p_t$ dependence.