e+e−→bbˉudˉμ−νˉμe^+e^- \to b \bar{b} u \bar{d} \mu^- \bar{\nu}_\mu with a ttˉt\bar{t} production

The cross section of $e^+e^- \to b \bar{b} u \bar{d} \mu^- \bar{\nu}_\mu$ process with a complete set of tree diagrams, 232 diagrams in the unitary gauge, was calculated at the energy range of $\sqrt{s}$ = 340 - 500 GeV by using GRACE system. A main contribution to the cross section comes from $t\bar{t}$ production, where $t$ and $\bar{t}$ decay into $bu\bar{d}$ and $\bar{b} \mu^- \bar{\nu}_{\mu}$, respectively. It was found that the interference between the diagrams with $t\bar{t}$ production and those with single-$t$ through $WW$ pair production amounts to 10% at the $t \bar{t}$ threshold energy region. In the energy region above twice of the top quark mass, more than 95% of the cross section comes from the $t\bar{t}$ diagrams.Comment: 17 pages, 8 PostScript figures, LateX; To appear in Phys. Lett.

Highlights from the SOAP project survey. What Scientists Think about Open Access Publishing

The SOAP (Study of Open Access Publishing) project has run a large-scale survey of the attitudes of researchers on, and the experiences with, open access publishing. Around forty thousands answers were collected across disciplines and around the world, showing an overwhelming support for the idea of open access, while highlighting funding and (perceived) quality as the main barriers to publishing in open access journals. This article serves as an introduction to the survey and presents this and other highlights from a preliminary analysis of the survey responses. To allow a maximal re-use of the information collected by this survey, the data are hereby released under a CC0 waiver, so to allow libraries, publishers, funding agencies and academics to further analyse risks and opportunities, drivers and barriers, in the transition to open access publishing.Comment: Data manual available at http://bit.ly/gI8nct Compressed CSV data file available at http://bit.ly/gSmm71 Alternative data formats: CSV http://bit.ly/ejuvKO XLS http://bit.ly/e6gE7o XLSX http://bit.ly/gTjyv

Testing the Higgs Sector of the Minimal Supersymmetric Standard Model at Large Hadron Colliders

We study the Higgs sector of the Minimal Supersymmetric Standard Model, in the context of proton-proton collisions at LHC and SSC energies. We assume a relatively heavy supersymmetric particle spectrum, and include recent results on one-loop radiative corrections to Higgs-boson masses and couplings. We begin by discussing present and future constraints from the LEP experiments. We then compute branching ratios and total widths for the neutral ($h,H,A$) and charged ($H^\pm$) Higgs particles. We present total cross-sections and event rates for the important discovery channels at the LHC and SSC. Promising physics signatures are given by $h \to \gamma \gamma$, $H \to \gamma \gamma$ or $Z^* Z^*$ or $\tau^+ \tau^-$, $A \to \tau^+ \tau^-$, and $t \to b H^+$ followed by $H^+ \to \tau^+ \nu_{\tau}$, which should allow for an almost complete coverage of the parameter space of the model.Comment: 51 pages, 30 figures (not enclosed and not available via e-mail

A gobal fit to the anomalous magnetic moment, b->s gamma and Higgs limits in the constrained MSSM

New data on the anomalous magnetic moment a_mu of the muon together with the b->s gamma decay rate are considered within the supergravity inspired constrained minimal supersymmetric model. We perform a global statistical chi^2 analysis of these data and show that the allowed region of parameter space is bounded from below by the Higgs limit, which depends on the trilinear coupling and from above by the anomalous magnetic moment a_mu. The newest b->s gamma data deviate 1.7 sigma from recent SM calculations and prefer a similar parameter region as the 2.6 sigma deviation from a_mu.Comment: 12 pages, 7 figs. Refs. update

The Stau Neutralino Co-annihilation Region at an International Linear Collider

We probe the stau-neutralino co-annihilation domain of the parameter space allowed by the current experimental bounds on the light Higgs mass, the b-> s \gamma decay, and the amount of neutralino cold dark matter within the framework of minimal SUGRA models at a 500 GeV e+e- linear collider. The most favorable signals of SUSY are stau pair production and neutralino pair production where the small mass difference between the lighter stau and the lightest neutralino in the co-annihilation region is ~5-15 GeV and hence generates low-energy tau leptons in the final state. This small mass difference would be a striking signal of many SUGRA models. We find that a calorimeter covering down to 1^o from the beams is crucial to reduce the two-photon background and the mass difference could be measured at a level of 10% with 500 fb^-1 of data where an invariant mass of two-tau jets and missing energy is used as a discriminator.Comment: 17 pages, 7 figure

How Finely Tuned is Supersymmetric Dark Matter?

We introduce a quantification of the question in the title: the logarithmic sensitivity of the relic neutralino density Omega-hsquared to variations in input parameters such as the supersymmetric mass scales m_0, m_1/2 and A_0, tan beta and the top and bottom quark masses. In generic domains of the CMSSM parameter space with a relic density in the preferred range 0.1 < Omega-hsquared < 0.3, the sensitivities to all these parameters are moderate, so an interesting amount of supersymetric dark matter is a natural and robust prediction. Within these domains, the accuracy in measuring the CMSSM and other input parameters at the LHC may enable the relic density to be predicted quite precisely. However, in the coannihilation regions, this might require more information on the supersymetric spectrum than the LHC is able to provide. There are also exceptional domains, such as those where direct-channel pole annihilation dominates, and in the `focus-point' region, where the logarithmic sensitivity to the input parameters is greatly increased, and it would be more difficult to predict Omega-hsquared accurately.Comment: 14 pages, 2 eps figure

Implications of a possible 115 GeV supersymmetric Higgs boson on detection and cosmological abundance of relic neutralinos

We show that a supersymmetric neutral Higgs boson with a mass of about 115 GeV and with the other prerequisites required by the LEP Higgs events would be compatible with the detection of relic neutralinos in current set-ups for WIMP direct search. Thus this putative Higgs would fit remarkably well in an interpretation in terms of relic neutralinos of the annual-modulation effect recently measured in a WIMP direct experiment. We also show that the cosmological abundance of the relevant neutralinos reaches values of cosmological interest.Comment: 15 pages, 6 figures, typeset with ReVTeX. The new version containes extended analysis. In order to reduce size, the version on the archive has low-resolution figures. The paper with high-resolution figures can be found at http://www.to.infn.it/~fornengo/papers

CP-Violating Lepton-Energy Correlation in e\bar{e}\to t\bar{t}

In order to observe a signal of possible CP violation in top-quark couplings, we have studied energy correlation of the final leptons in $e^+e^-\to t\bar{t} \to \ell^+\ell^-X / \ell^\pm X$ at future linear colliders. Applying the recently-proposed optimal method, we have compared the statistical significances of CP-violation-parameter determination using double- and single-lepton distributions. We have found that the single-lepton-distribution analysis is more advantageous.Comment: Final version (to appear in Phys.Lett.B

Direct Higgs production and jet veto at the Tevatron and the LHC in NNLO QCD

We consider Higgs boson production through gluon--gluon fusion in hadron collisions, when a veto is applied on the transverse momenta of the accompanying hard jets. We compute the QCD radiative corrections to this process at NLO and NNLO. The NLO calculation is complete. The NNLO calculation uses the recently evaluated NNLO soft and virtual QCD contributions to the inclusive cross section. We find that the jet veto reduces the impact of the NLO and NNLO contributions, the reduction being more sizeable at the LHC than at the Tevatron.Comment: 22 pages, 12 postscript figure