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An update on the next-to-leading order Monte Carlo MCFM
The current status of the parton level, next-to-leading order Monte Carlo program MCFM is described
Metastable Charged Sparticles and the Cosmological Li7 Problem
We consider the effects of metastable charged sparticles on Big-Bang
Nucleosynthesis (BBN), including bound-state reaction rates and chemical
effects. We make a new analysis of the bound states of negatively-charged
massive particles with the light nuclei most prominent in BBN, and present a
new code to track their abundances, paying particular attention to that of Li7.
Assuming, as an example, that the gravitino is the lightest supersymmetric
particle (LSP), and that the lighter stau slepton, stau_1, is the metastable
next-to-lightest sparticle within the constrained minimal supersymmetric
extension of the Standard Model (CMSSM), we analyze the possible effects on the
standard BBN abundances of stau_1 bound states and decays for representative
values of the gravitino mass. Taking into account the constraint on the CMSSM
parameter space imposed by the discovery of the Higgs boson at the LHC, we
delineate regions in which the fit to the measured light-element abundances is
as good as in standard BBN. We also identify regions of the CMSSM parameter
space in which the bound state properties, chemistry and decays of metastable
charged sparticles can solve the cosmological Li7 problem.Comment: 49 pages, 29 eps figure
Nuclear Reaction Uncertainties, Massive Gravitino Decays and the Cosmological Lithium Problem
We consider the effects of uncertainties in nuclear reaction rates on the
cosmological constraints on the decays of unstable particles during or after
Big-Bang nucleosynthesis (BBN). We identify the nuclear reactions due to
non-thermal hadrons that are the most important in perturbing standard BBN,
then quantify the uncertainties in these reactions and in the resulting
light-element abundances. These results also indicate the key nuclear processes
for which improved cross section data would allow different light-element
abundances to be determined more accurately, thereby making possible more
precise probes of BBN and evaluations of the cosmological constraints on
unstable particles. Applying this analysis to models with unstable gravitinos
decaying into neutralinos, we calculate the likelihood function for the
light-element abundances measured currently, taking into account the current
experimental errors in the determinations of the relevant nuclear reaction
rates. We find a region of the gravitino mass and abundance in which the
abundances of deuterium, He4 and Li7 may be fit with chi^2 = 5.5, compared with
chi^2 = 31.7 if the effects of gravitino decays are unimportant. The best-fit
solution is improved to chi^2 ~ 2.0 when the lithium abundance is taken from
globular cluster data. Some such re-evaluation of the observed light-element
abundances and/or nuclear reaction rates would be needed if this region of
gravitino parameters is to provide a complete solution to the cosmological Li7
problem.Comment: 24 pages, 10 figure
Gravitino Decays and the Cosmological Lithium Problem in Light of the LHC Higgs and Supersymmetry Searches
We studied previously the impact on light-element abundances of gravitinos
decaying during or after Big-Bang nucleosynthesis (BBN). We found regions of
the gravitino mass m_{3/2} and abundance zeta_{3/2} plane where its decays
could reconcile the calculated abundance of Li7 with observation without
perturbing the other light-element abundances unacceptably. Here we revisit
this issue in light of LHC measurements of the Higgs mass and constraints on
supersymmetric model parameters, as well as updates in the astrophysical
measurements of light-element abundances. In addition to the constrained
minimal supersymmetric extension of the Standard Model with universal soft
supersymmetry-breaking masses at the GUT scale (the CMSSM) studied previously,
we also study models with universality imposed below the GUT scale and models
with non-universal Higgs masses (NUHM1). We calculate the total likelihood
function for the light-element abundances, taking into account the
observational uncertainties. We find that gravitino decays provide a robust
solution to the cosmological Li7 problem along strips in the (m_{3/2},
zeta_{3/2}) plane along which the abundances of deuterium, He4 and Li7 may be
fit with chi^2_min < 3, compared with chi^2 ~ 34 if the effects of gravitino
decays are unimportant. The minimum of the likelihood function is reduced to
chi^2 < 2 when the uncertainty on D/H is relaxed and < 1 when the lithium
abundance is taken from globular cluster data.Comment: 20 pages, 5 figures; added a new table and a discussion paragraph for
it in Section 4, matches the published versio
Supersymmetric Dark Matter in Light of WMAP
We re-examine the parameter space of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), taking account of the restricted range of \Omega_{CDM} h^2 consistent with the WMAP data. This provides a significantly reduced upper limit on the mass of the lightest supersymmetric particle LSP: m_\chi 0, or \tan \beta < 30 and \mu < 0, thereby improving the prospects for measuring supersymmetry at the LHC, and increasing the likelihood that a 1-TeV linear e^+ e^- collider would be able to measure the properties of some supersymmetric particles
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