242 research outputs found
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, factorization including low-
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 TeV and at 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 to
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.Comment: 61 pages, 25 figures, 11 table
Constraining the primordial spectrum of metric perturbations from gravitino and moduli production
We consider the production of gravitinos and moduli fields from quantum
vacuum fluctuations induced by the presence of scalar metric perturbations at
the end of inflation. We obtain the corresponding occupation numbers, up to
first order in perturbation theory, in terms of the power spectrum of the
metric perturbations. We compute the limits imposed by nucleosynthesis on the
spectral index for different models with constant . The results show
that, in certain cases, such limits can be as strong as , which is
more stringent than those coming from primordial black hole production.Comment: 16 pages, LaTeX, 5 figures. Corrected figures, new references
included. Final version to appear in Phys. Rev.
Cosmic Strings and the String Dilaton
The existence of a dilaton (or moduli) with gravitational-strength coupling
to matter imposes stringent constraints on the allowed energy scale of cosmic
strings, . In particular, superheavy gauge strings with are ruled out unless the dilaton mass m_{\phi} \gsim 100 TeV,
while the currently popular value imposes the bound \eta
\lsim 3 \times 10^{11} GeV. Similar constraints are obtained for global
topological defects. Some non-standard cosmological scenarios which can avoid
these constraints are pointed out.Comment: 16 page
Production and dilution of gravitinos by modulus decay
We study the cosmological consequences of generic scalar fields like moduli
which decay only through gravitationally suppressed interactions. We consider a
new production mechanism of gravitinos from moduli decay, which might be more
effective than previously known mechanisms, and calculate the final
gravitino-to-entropy ratio to compare with the constraints imposed by
successful big bang nucleosynthesis (BBN) etc., taking possible hadronic decays
of gravitinos into account. We find the modulus mass smaller than
TeV is excluded. On the other hand, inflation models with high reheating
temperatures GeV can be compatible with BBN thanks
to the late-time entropy production from the moduli decay if model parameters
are appropriately chosen.Comment: 18 pages, 4 figures, to appear in Phys. Rev.
MeV-scale Reheating Temperature and Thermalization of Neutrino Background
The late-time entropy production by the massive particle decay induces the
various cosmological effects in the early epoch and modify the standard
scenario. We investigate the thermalization process of the neutrinos after the
entropy production by solving the Boltzmann equations numerically. We find that
if the large entropy are produced at t 1 sec, the neutrinos are not
thermalized very well and do not have the perfect Fermi-Dirac distribution.
Then the freeze-out value of the neutron to proton ratio is altered
considerably and the produced light elements, especially He4, are drastically
changed. Comparing with the observational light element abundances, we find
that < 0.7 MeV is excluded at 95 % C.L. We also study the case in which
the massive particle has a decay mode into hadrons. Then we find that
should be a little higher, i.e. > 2.5 MeV - 4 MeV, for the hadronic
branching ratio . Possible influence of late-time entropy
production on the large scale structure formation and temperature anisotropies
of cosmic microwave background is studied. It is expected that the future
satellite experiments (MAP and PLANCK) to measure anisotropies of cosmic
microwave background radiation temperature can detect the vestige of the
late-time entropy production as a modification of the effective number of the
neutrino species .Comment: 43 pages, using REVTEX and 17 postscript figure
False Vacuum Inflation with Einstein Gravity
We investigate chaotic inflation models with two scalar fields, such that one
field (the inflaton) rolls while the other is trapped in a false vacuum state.
The false vacuum becomes unstable when the inflaton field falls below some
critical value, and a first or second order transition to the true vacuum
ensues. Particular attention is paid to Linde's second-order `Hybrid
Inflation'; with the false vacuum dominating, inflation differs from the usual
true vacuum case both in its cosmology and in its relation to particle physics.
The spectral index of the adiabatic density perturbation can be very close to
1, or it can be around ten percent higher. The energy scale at the end of
inflation can be anywhere between \,GeV and \,GeV, though
reheating is prompt so the reheat temperature can't be far below
GeV. Topological defects are almost inevitably produced at the end
of inflation, and if the inflationary energy scale is near its upper limit they
can have significant effects.
Because false vacuum inflation occurs with the inflaton field far below the
Planck scale, it is easier to implement in the context of supergravity than
standard chaotic inflation. That the inflaton mass is small compared with the
inflationary Hubble parameter is still a problem for generic supergravity
theories, but remarkably this can be avoided in a natural way for a class of
supergravity models which follow from orbifold compactification of
superstrings. This opens up the prospect of a truly realistic, superstringComment: 37 pages, LaTeX (3 figures available as hard copies only), SUSSEX-AST
94/1-
Anatomical Network Comparison of Human Upper and Lower, Newborn and Adult, and Normal and Abnormal Limbs, with Notes on Development, Pathology and Limb Serial Homology vs. Homoplasy
How do the various anatomical parts (modules) of the animal body evolve into very different integrated forms (integration) yet still function properly without decreasing the individual's survival? This long-standing question remains unanswered for multiple reasons, including lack of consensus about conceptual definitions and approaches, as well as a reasonable bias toward the study of hard tissues over soft tissues. A major difficulty concerns the non-trivial technical hurdles of addressing this problem, specifically the lack of quantitative tools to quantify and compare variation across multiple disparate anatomical parts and tissue types. In this paper we apply for the first time a powerful new quantitative tool, Anatomical Network Analysis (AnNA), to examine and compare in detail the musculoskeletal modularity and integration of normal and abnormal human upper and lower limbs. In contrast to other morphological methods, the strength of AnNA is that it allows efficient and direct empirical comparisons among body parts with even vastly different architectures (e.g. upper and lower limbs) and diverse or complex tissue composition (e.g. bones, cartilages and muscles), by quantifying the spatial organization of these parts-their topological patterns relative to each other-using tools borrowed from network theory. Our results reveal similarities between the skeletal networks of the normal newborn/adult upper limb vs. lower limb, with exception to the shoulder vs. pelvis. However, when muscles are included, the overall musculoskeletal network organization of the upper limb is strikingly different from that of the lower limb, particularly that of the more proximal structures of each limb. Importantly, the obtained data provide further evidence to be added to the vast amount of paleontological, gross anatomical, developmental, molecular and embryological data recently obtained that contradicts the long-standing dogma that the upper and lower limbs are serial homologues. In addition, the AnNA of the limbs of a trisomy 18 human fetus strongly supports Pere Alberch's ill-named "logic of monsters" hypothesis, and contradicts the commonly accepted idea that birth defects often lead to lower integration (i.e. more parcellation) of anatomical structures
Leptogenesis from -dominated early universe
We investigate in detail the leptogenesis by the decay of coherent
right-handed sneutrino having dominated the energy density of
the early universe, which was originally proposed by HM and TY. Once the
dominant universe is realized, the amount of the generated
lepton asymmetry (and hence baryon asymmetry) is determined only by the
properties of the right-handed neutrino, regardless of the history before it
dominates the universe. Moreover, thanks to the entropy production by the decay
of the right-handed sneutrino, thermally produced relics are sufficiently
diluted. In particular, the cosmological gravitino problem can be avoided even
when the reheating temperature of the inflation is higher than 10^{10}\GeV,
in a wide range of the gravitino mass m_{3/2}\simeq 10\MeV--100\TeV. If the
gravitino mass is in the range m_{3/2}\simeq 10\MeV--1\GeV as in the some
gauge-mediated supersymmetry breaking models, the dark matter in our universe
can be dominantly composed of the gravitino. Quantum fluctuation of the
during inflation causes an isocurvature fluctuation which may
be detectable in the future.Comment: 16 page
Tau Neutrinos in the Next Decade: from GeV to EeV
Tau neutrinos are the least studied particle in the Standard Model. Thiswhitepaper discusses the current and expected upcoming status of tau neutrinophysics with attention to the broad experimental and theoretical landscapespanning long-baseline, beam-dump, collider, and astrophysical experiments.This whitepaper was prepared as a part of the NuTau2021 Workshop.<br
Production properties of K*(892) vector mesons and their spin alignment as measured in the NOMAD experiment
First measurements of K*(892) mesons production properties and their spin
alignment in nu_mu charged current (CC) and neutral current (NC) interactions
are presented. The analysis of the full data sample of the NOMAD experiment is
performed in different kinematic regions. For K*+ and K*- mesons produced in
nu_mu CC interactions and decaying into K0 pi+/- we have found the following
yields per event: (2.6 +/- 0.2 (stat.) +/- 0.2 (syst.))% and (1.6 +/- 0.1
(stat.) +/- 0.1 (syst.))% respectively, while for the K*+ and K*- mesons
produced in nu NC interactions the corresponding yields per event are: (2.5 +/-
0.3 (stat.) +/- 0.3 (syst.))% and (1.0 +/- 0.3 (stat.) +/- 0.2 (syst.))%. The
results obtained for the rho00 parameter, 0.40 +/- 0.06 (stat) +/- 0.03 (syst)
and 0.28 +/- 0.07 (stat) +/- 0.03 (syst) for K*+ and K*- produced in nu_mu CC
interactions, are compared to theoretical predictions tuned on LEP measurements
in e+e- annihilation at the Z0 pole. For K*+ mesons produced in nu NC
interactions the measured rho00 parameter is 0.66 +/- 0.10 (stat) +/- 0.05
(syst).Comment: 20 p
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