14 research outputs found
A Bayesian view of the current status of dark matter direct searches
Bayesian statistical methods offer a simple and consistent framework for
incorporating uncertainties into a multi-parameter inference problem. In this
work we apply these methods to a selection of current direct dark matter
searches. We consider the simplest scenario of spin-independent elastic WIMP
scattering, and infer the WIMP mass and cross-section from the experimental
data with the essential systematic uncertainties folded into the analysis. We
find that when uncertainties in the scintillation efficiency of Xenon100 have
been accounted for, the resulting exclusion limit is not sufficiently
constraining to rule out the CoGeNT preferred parameter region, contrary to
previous claims. In the same vein, we also investigate the impact of
astrophysical uncertainties on the preferred WIMP parameters. We find that
within the class of smooth and isotropic WIMP velocity distributions, it is
difficult to reconcile the DAMA and the CoGeNT preferred regions by tweaking
the astrophysics parameters alone. If we demand compatibility between these
experiments, then the inference process naturally concludes that a high value
for the sodium quenching factor for DAMA is preferred.Comment: 37 pages, 14 figures and 7 tables. Replacement for matching the
version accepted for publicatio
Supernova neutrino oscillations: A simple analytical approach
Analyses of observable supernova neutrino oscillation effects require the
calculation of the electron (anti)neutrino survival probability P_ee along a
given supernova matter density profile. We propose a simple analytical
prescription for P_ee, based on a double-exponential form for the crossing
probability and on the concept of maximum violation of adiabaticity. In the
case of two-flavor transitions, the prescription is shown to reproduce
accurately, in the whole neutrino oscillation parameter space, the results of
exact numerical calculations for generic (realistic or power-law) profiles. The
analytical approach is then generalized to cover three-flavor transitions with
(direct or inverse) mass spectrum hierarchy, and to incorporate Earth matter
effects. Compact analytical expressions, explicitly showing the symmetry
properties of P_ee, are provided for practical calculations.Comment: 22 pages (RevTeX) + 5 figures (PostScript
SN1987A and the Status of Oscillation Solutions to the Solar Neutrino Problem (including an appendix discussing the NC and day/night data from SNO)
We study neutrino oscillations and the level-crossing probability PLZ in
power-law potential profiles A(r)\propto r^n. We give local and global
adiabaticity conditions valid for all mixing angles theta and discuss different
representations for PLZ. For the 1/r^3 profile typical of supernova envelopes
we compare our analytical to numerical results and to earlier approximations
used in the literature. We then perform a combined likelihood analysis of the
observed SN1987A neutrino signal and of the latest solar neutrino data,
including the recent SNO CC measurement. We find that, unless all relevant
supernova parameters (released binding energy, \bar\nu_e and \bar\nu_{\mu,\tau}
temperatures) are near their lowest values found in simulations, the status of
large mixing type solutions deteriorates considerably compared to fits using
only solar data. This is sufficient to rule out the vacuum-type solutions for
most reasonable choices of astrophysics parameters. The LOW solution may still
be acceptable, but becomes worse than the SMA-MSW solution which may, in some
cases, be the best combined solution. On the other hand the LMA-MSW solution
can easily survive as the best overall solution, although its size is generally
reduced when compared to fits to the solar data only.Comment: 31 pages, 32 eps figures; 5 pages, 5 eps figures addendum in v2,
discussing the recent SNO NC data and changes in SN paramete
Relic neutrino masses and the highest energy cosmic rays
We consider the possibility that a large fraction of the ultrahigh energy
cosmic rays are decay products of Z bosons which were produced in the
scattering of ultrahigh energy cosmic neutrinos on cosmological relic
neutrinos. We compare the observed ultrahigh energy cosmic ray spectrum with
the one predicted in the above Z-burst scenario and determine the required mass
of the heaviest relic neutrino as well as the necessary ultrahigh energy cosmic
neutrino flux via a maximum likelihood analysis. We show that the value of the
neutrino mass obtained in this way is fairly robust against variations in
presently unknown quantities, like the amount of neutrino clustering, the
universal radio background, and the extragalactic magnetic field, within their
anticipated uncertainties. Much stronger systematics arises from different
possible assumptions about the diffuse background of ordinary cosmic rays from
unresolved astrophysical sources. In the most plausible case that these
ordinary cosmic rays are protons of extragalactic origin, one is lead to a
required neutrino mass in the range 0.08 eV - 1.3 eV at the 68 % confidence
level. This range narrows down considerably if a particular universal radio
background is assumed, e.g. to 0.08 eV - 0.40 eV for a large one. The required
flux of ultrahigh energy cosmic neutrinos near the resonant energy should be
detected in the near future by AMANDA, RICE, and the Pierre Auger Observatory,
otherwise the Z-burst scenario will be ruled out.Comment: 19 pages, 22 figures, REVTeX
Exploring the sub-eV neutrino mass range with supernova neutrinos
A new method to study the effects of neutrino masses on a supernova neutrino
signal is proposed. The method relies exclusively on the analysis of the full
statistics of neutrino events, it is independent of astrophysical assumptions,
and does not require the observation of any additional phenomenon to trace
possible delays in the neutrino arrival times. The sensitivity of the method to
the sub-eV neutrino mass range, defined as the capability of disentangling at
95% c.l. the case eV from , is tested by analyzing a set of
synthetic neutrino samples modeled according to the signal that could be
detected at SuperKamiokande. For a supernova at the Galactic center success is
achieved in more than 50% of the cases. It is argued that a future Galactic
supernova yielding several thousands of inverse decays might provide
enough information to explore a neutrino mass range somewhat below 1 eV.Comment: Included analysis with numerical neutrino energy spectrum and
oscillations effects. 7 pages, 6 figure
SN1987A and the properties of neutrino burst
We reanalyze the neutrino events from SN1987A in IMB and Kamiokande-II (KII)
detectors, and compare them with the expectations from simple theoretical
models of the neutrino emission. In both detectors the angular distributions
are peaked in the forward direction, and the average cosines are 2 sigma above
the expected values. Furthermore, the average energy in KII is low if compared
with the expectations; but, as we show, the assumption that a few (probably
one) events at KII have been caused by elastic scattering is not in contrast
with the 'standard' picture of the collapse and yields a more satisfactory
distributions in angle and (marginally) in energy. The observations give useful
information on the astrophysical parameters of the collapse: in our
evaluations, the mean energy of electron antineutrinos is =12-16 MeV, the
total energy radiated around (2-3)*1.E53 erg, and there is a hint for a
relatively large radiation of non-electronic neutrino species. These properties
of the neutrino burst are not in disagreement with those suggested by the
current theoretical paradigm, but the data leave wide space to non-standard
pictures, especially when neutrino oscillations are included.Comment: 14 pages, 5 figure
A Markov chain Monte Carlo analysis of the CMSSM
We perform a comprehensive exploration of the Constrained MSSM parameter space employing a Markov Chain Monte Carlo technique and a Bayesian analysis. We compute superpartner masses and other collider observables, as well as a cold dark matter abundance, and compare them with experimental data. We include uncertainties arising from theoretical approximations as well as from residual experimental errors of relevant Standard Model parameters. We delineate probability distributions of the CMSSM parameters, the collider and cosmological observables as well as a dark matter direct detection cross section. The 68% probability intervals of the CMSSM parameters are: 0.52 TeV < m1/2 < 1.26 TeV, m0 < 2.10 TeV, -0.34 TeV < A0 < 2.41 TeV and 38.5 < tan \u3b2 < 54.6. Generally, large fractions of high probability ranges of the superpartner masses will be probed at the LHC. For example, we find that the probability of mg < 2.7TeV is 78%, of mqR < 2.5TeV is 85% and of m\u3c7\ub11 < 0.8TeV is 65%. As regards the other observables, for example at 68% probability we find 3.5
710-9 < BR(Bs \u2192 \u3bc+\u3bc-) < 1.7
710-8, 1.9
710-10 < \u3b4a SUSY \u3bc < 9.9
710-10 and 1
7 10 -10 pb < \u3c3SIp < 1
7 10 -8 pb for direct WIMP detection. We highlight a complementarity between LHC and WIMP dark matter searches in exploring the CMSSM parameter space. We further expose a number of correlations among the observables, in particular between BR(Bs \u2192 \u3bc+\u3bc-) and BR(B \u2192 X s\u3b3) or \u3c3SIp. Once SUSY is discovered, this and other correlations may prove helpful in distinguishing the CMSSM from other supersymmetric models. We investigate the robustness of our results in terms of the assumed ranges of CMSSM parameters and the effect of the (g - 2)\u3bc anomaly which shows some tension with the other observables. We find that the results for m0, and the observables which strongly depend on it, are sensitive to our assumptions, while our conclusions for the other variables are robust