On b- and tau-multiplicities per event in SUSY (mSUGRA) and instrumental implications

We investigate the probability to find a b or tau in SUSY production with the mSUGRA model. We find that in the entire parameter space the probability per event to find a b-jet of E_T^b > 50 GeV within CMS acceptance (eta < 2.4) is significant for all tan(beta), varying from a 10 % level to 90 % depending on the m_0, m_1/2 region. The probabilities per event to find a tau with the same kinematical cuts is also significant and it increases sharply with tan(beta). These findings point to the central role a microvertex device would play in case that SUSY (mSUGRA) is indeed realized in nature and found at the LHC. First investigations done in the context of the more general MSSM scenario confirm the findings based on mSUGRA.Comment: 19 pages, 13 figures, 3 table

Observability of MSSM Higgs bosons via sparticle decay modes in CMS

We discuss the possibilities to observe the decays of heavy SUSY Higgs bosons into supersymmetric particles at the LHC. Such an observation would be of interest either in a discovery search if sparticle modes are the dominant ones, or in a study of additional decay modes, bringing information on the SUSY scenario potentially at work. We will focus on the most promising channel where the heavy neutral Higgses decay into a pair of next-to-lightest neutralinos, followed by their decay into two leptons and the LSP, thus leading to four isolated leptons + missing E_T as the main final state signature. A study with the CMS detector shows that the background (SM + SUSY) can be sufficiently suppressed and that in the mass region between m_A = 230 and 450 GeV, for low and intermediate values of tan beta, the signal would be visible provided neutralinos and sleptons are light enough.Comment: 14 pages, 20 figure

Study of leptoquark pair production at the LHC with the CMS detector

We study the discovery potential of the CMS detector for the scalar leptoquark pair production at the LHC. Present and future exclusion limits are considered. We find that the maximal leptoquark mass reach is about 1.47 TeV for the branching ratio of Br(LQ_l -> l q)=100 %, while for Br(LQ_l -> l q)=50 % the upper limit is 1.2 TeV for an integrated luminosity of 100 fb-1. We obtain comparable results for electron and muon-type leptoquarks. The pileup effect at high luminosity is discussed.Comment: 10 pages, 7 figures, 4 tables, UNIX LaTe

Diphoton Background to Higgs Boson Production at the LHC with Soft Gluon Effects

The detection and the measurement of the production cross section of a light Higgs boson at the CERN Large Hadron Collider demand the accurate prediction of the background distributions of photon pairs. To improve this theoretical prediction, we present the soft-gluon resummed calculation of the $p p \to \gamma \gamma X$ cross section, including the exact one loop $g g \to \gamma \gamma g$ contribution. By incorporating the known fixed order results and the leading terms in the higher order corrections, the resummed cross section provides a reliable prediction for the inclusive diphoton invariant mass and transverse momentum distributions. Given our results, we propose the search for the Higgs boson in the inclusive diphoton mode with a cut on the transverse momentum of the photon pair, without the requirement of an additional tagged jet.Comment: 5 pages, 4 figures. A figure with discussion, and a reference added. Minor improvements of wording. Conclusion unchange

Effects of using metamaterial in waveguide design

Исследовано понятие метаматериала, описывается его суть, приведены свойства и причины их возникновения. Представлены различные варианты исполнения метаматериалов, дана методика расчета их резонансной частоты. Вводятся понятия отрицательной групповой скорости, левой среды, прямой и обратной волн. Исследованы эффекты применения метаматериалов в конструкциях волноводов различного рода и форм поперечного сечения. Проанализировано влияние ориентации включений относительно падающей волны на характеристики направляющей структуры. Сделан вывод о возможности использования волновода, заполненного метаматериалом, в основе конструкции антенны вытекающих волн.A concept of metamaterials is investigated, its essence is described, properties and its causes are shown. Different versions of metamaterials are presented, and calculation method of resonant frequency is given. The concepts of negative group velocity, left-handed media, forward and backward wave are introduced. Effects of using metamaterials in design of the various waveguides with the different cross section form are investigated. An influence of inclusions orientation relative to an incident wave on the guided structure performances is analyzed. The conclusion about possibility of using metamaterial loaded waveguide as a leaky-wave antenna base is made

Search for SUSY in (Leptons +) Jets + E_T^miss final states

We study the observability of the squarks and gluinos in CMS at LHC. Classical E_T^miss + jets final state as well as a number of additional multilepton signatures (0 leptons, 1 lepton, 2 leptons of the same sign, 2 leptons of the opposite sign and 3 leptons) are investigated . The detection of these sparticles relies on the observation of an excess of events over Standard Model background expectations. The study is made in the framework of a minimal SU(5) mSUGRA model as a function of m_0, m_1/2 for 4 sets of model parameters : tan(beta) = 2 or 35 and sign(mu) = +/- 1 and for fixed value of A_0 = 0. The CMS detector response is modelled using CMSJET 4.51 fast MC code (non-GEANT). The results obtained are presented as 5 sigma detection contours in the m_0, m_1/2 planes and with optimized selection cuts in various regions of the parameter space. The result of these investigations is that with integrated luminosity L=10^5 pb^-1 the squark and gluino mass reach is about 2.5 TeV and covers most of the interesting parts of parameter space according to neutralino relic density expectations. The influence of signal and background cross-section uncertainties on the reach contours is estimated. The effect of pile-up on signal and background is also discussed. This effect is found to be insignificant for E_T^miss and single lepton signatures, whilst only a minor deterioration is seen for multilepton final states.Comment: 28 pages, 28 figure

Two photons plus jet al LHC: the NNLO contribution from the gg initiated process

The production of the Standard Model Higgs boson of mass ~ 100-140 GeV at the LHC likely gives clear signals in the $\gamma \gamma$ (1) and in the $\gamma \gamma jet$ (2) channels. The quantitative evaluation of the background to channel (1) is very hard since the next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) QCD corrections are large. In particular, the contributions of the NNLO QCD subprocess $gg -> \gamma \gamma$ to inclusive $\gamma\gamma$ production is comparable to the contribution of the leading order subprocess $q\bar{q} -> \gamma \gamma$. The quantitative description of the background to channel (1), therefore, requires to calculate all corrections up to the NNNLO level. In this letter we present results on the contribution of the NNLO QCD subprocess $gg -> g \gamma \gamma$ to the production rate of channel (2). We have found that in this case this NNLO contribution is less than 20% of the Born contribution. Since the NNLO contributions will likely be dominated by this subprocess one can argue that in the case of channel (2) - contrary to the case of channel (1)- a quantitative description of the background can be achieved already at next-to-leading order accuracy.Comment: 7 pages, two figures include

Sgoldstino events in top decays at LHC

We study top-quark decays in models with light sgoldstinos. The off-diagonal entries in the squark mass matrices can lead to FCNC top two-body decays into sgoldstinos and u(c) quarks. We compute the rates for these decays and discuss the corresponding signatures that could manifest the presence of sgoldstinos in top decays at LHC. We expect that a supersymmetry breaking scale $\sqrt{F}$ up to a scale of order 10 TeV could be probed through this process, for a maximal squark mixing with the third generation. Justified by our preliminary analysis, a thorough study of the corresponding signal versus background and systematics in the LHC environment would be most welcome, in order to accurately assess the potential of this promising process in determining $\sqrt{F}$.Comment: Standard LaTeX, 11 pages, 4 figures, one reference adde

Neutralino Dark Matter in Focus Point Supersymmetry

In recent work, it has been argued that multi-TeV masses for scalar superpartners are not unnatural. Indeed, they appear to have significant phenomenological virtues. Here we explore the implications of such `focus point' supersymmetry for the dark matter problem. We find that constraints on relic densities do not place upper bounds on neutralino or scalar masses. We demonstrate that, in the specific context of minimal supergravity, a cosmologically stable mixed gaugino-Higgsino state emerges as an excellent, robust dark matter candidate. We estimate that, over a wide range of the unknown parameters, the spin-independent proton-neutralino cross sections fall in the range accessible to planned search experiments.Comment: 15 pages, 6 figures, version to appear in Phys. Lett. B. References added, minor modifications of Figs. 2 and 4 due to a bug (sign error) in neutdrive

GARCON - Genetic Algorithm for Rectangular Cuts OptimizatioN.

We will present Genetic Algorithm for Rectangular Cuts OptimizatioN (GARCON) program and demonstrate its functionality on a simple HEP analysis example. The program automatically performs rectangular cuts optimization and verification for stability in a multi-dimensional cuts phase space. The program has been successfully used by a number of different analyses presented in the Compact Muon Solenoid (CMS collaboration) Physics Technical Design Report (Large Hadron Collider (LHC), CERN, Geneva, Switzerland), corresponding results are also published in a number of papers in 2006