Production and Two-photon Decay of the MSSM Scalar Higgs Bosons at the LHC

We consider the production and two-photon decay of the $CP$-even Higgs bosons ($h^0$ and $H^0$) of the Minimal Supersymmetric Standard Model (MSSM) at the Large Hadron Collider. We study in detail the dependence of the cross section on various parameters of the MSSM, especially the dependence on the mixing effects in the squark sector due to the Higgs bilinear parameter $\mu$ and the soft supersymmetry breaking parameter $A$. We find that the cross section for the production of these Higgs bosons has a significant dependence on the parameters which determine the chiral mixing in the squark sector. The cross section times the two-photon branching ratio of $h^0$ is of the order of 15--25~fb in much of the parameter space that remains after imposing the present experimental constraints. For the $H^0$ the two-photon branching ratio is only significant if the $H^0$ is light, but then the cross section times the branching ratio may exceed 200~fb. The QCD corrections due to quark loop contributions are known to increase the cross section by 50\%. We find the dependence of the cross section on the gluon distribution function used to be rather insignificant.Comment: 16 pages, LaTex, plus 9 uuencoded figures attached Full ps file available at ftp://vsfys1.fi.uib.no/anonymous/pub/ as nordita-9548.ps or nordita-9548.ps-gz or via http://vsfys1.fi.uib.no/thpubl/publications.htm

Light, long-lived and secluded: can gluinos be driven out from LEP1 data ?

We briefly report about a possible settlement of the still ongoing dispute concerning the existence of SUSY signals in 4jet events at LEP1. We base our arguments on a simple selection strategy exploiting secondary vertex tagging and kinematical constraints, which could allow one to access or exclude gluino events for a broad range of masses and lifetimes.Comment: 10 pages, LaTeX, 3 PostScript figures embedded with epsfig. Complete ps paper and figures available also at ftp://ftae3.ugr.es/pub/rmt/ugrft70.p

Gluino Pair Production at Linear e^+e^- Colliders

We study the potential of high-energy linear $e^+e^-$ colliders for the production of gluino pairs within the Minimal Supersymmetric Standard Model (MSSM). In this model, the process $e^+e^-\to\tilde{g}\tilde{g}$ is mediated by quark/squark loops, dominantly of the third generation, where the mixing of left- and right-handed states can become large. Taking into account realistic beam polarization effects, photon and $Z^0$-boson exchange, and current mass exclusion limits, we scan the MSSM parameter space for various $e^+e^-$ center-of-mass energies to determine the regions, where gluino production should be visible.Comment: 22 pages, 9 figure

Gluino Production in Electron-Positron Annihilation

We discuss the pair production of gluinos in electron-positron annihilation at LEP, in a model with soft supersymmetry breaking, allowing for mixing between the squarks. In much of the parameter space of the Minimal Supersymmetric Model (MSSM) the cross section corresponds to a $Z$ branching ratio above $10^{-5}$, even up to $10^{-4}$. A non-observation of gluinos at this level restricts the allowed MSSM parameter space. In particular, it leads to lower bounds on the soft mass parameters in the squark sector.Comment: 24 pages LATEX plus 10 pages of figures (not included, available on request). Full postscript version available by anonymous ftp at node VSFYS1.FI.UIB.NO in subdirectory OSLAND, file BERGEN94-10.PS), Bergen Scientific/Technical Report No. 1994-1

Rompimiento de la Simetria Electrodebil y la Fisica del Higgs: Conceptos Basicos

Presentamos una introduccion a los conceptos basicos del rompimiento de la simetria electrodebil y la fisica del Higgs dentro del Modelo Estandar y sus extensiones supersimetricas. Se presenta tambien una breve perspectiva general de mecanismos alternativos del rompimiento de la simetria. Ademas de las bases teoricas, se discute el estado actual de la fisica experimental del Higgs y sus implicaciones para futuros experimentos en el LHC y en colisionadores lineales e+e-.Comment: Spanish text, including full English translation. Published in the Proceedings of the XI Mexican School on Particles and Fields, Xalapa, Veracruz, Mexic

MSSM Higgs-Boson Production at Hadron Colliders with Explicit CP Violation

Gluon fusion is the main production mechanism for Higgs bosons with masses up to several hundred GeV in $pp$ collisions at the CERN Large Hadron Collider. We investigate the effects of the CP-violating phases on the fusion process including both the sfermion-loop contributions and the one-loop induced CP-violating scalar-pseudoscalar mixing in the minimal supersymmetric standard model. With a universal trilinear parameter assumed, every physical observable involves only the sum of the phases of the universal trilinear parameter $A$ and the higgsino mass parameter $\mu$. The phase affects the lightest Higgs-boson production rate significantly through the neutral Higgs-boson mixing and, for the masses around the lightest stop-pair threshold, it also changes the production rate of the heavy Higgs bosons significantly through both the stop and sbottom loops and the neutral Higgs-boson mixing.Comment: 28 pages, 8 figures. Some references and comments added. Typos corrected. To appear in Phys. Rev.

Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at s=0.9\sqrt{s}=0.9, 2.76 and 7 TeV

Measurements of the sphericity of primary charged particles in minimum bias proton--proton collisions at $\sqrt{s}=0.9$, 2.76 and 7 TeV with the ALICE detector at the LHC are presented. The observable is linearized to be collinear safe and is measured in the plane perpendicular to the beam direction using primary charged tracks with $p_{\rm T}\geq0.5$ GeV/c in $|\eta|\leq0.8$. The mean sphericity as a function of the charged particle multiplicity at mid-rapidity ($N_{\rm ch}$) is reported for events with different $p_{\rm T}$ scales ("soft" and "hard") defined by the transverse momentum of the leading particle. In addition, the mean charged particle transverse momentum versus multiplicity is presented for the different event classes, and the sphericity distributions in bins of multiplicity are presented. The data are compared with calculations of standard Monte Carlo event generators. The transverse sphericity is found to grow with multiplicity at all collision energies, with a steeper rise at low $N_{\rm ch}$, whereas the event generators show the opposite tendency. The combined study of the sphericity and the mean $p_{\rm T}$ with multiplicity indicates that most of the tested event generators produce events with higher multiplicity by generating more back-to-back jets resulting in decreased sphericity (and isotropy). The PYTHIA6 generator with tune PERUGIA-2011 exhibits a noticeable improvement in describing the data, compared to the other tested generators.Comment: 21 pages, 9 captioned figures, 3 tables, authors from page 16, published version, figures from http://aliceinfo.cern.ch/ArtSubmission/node/308

Charge separation relative to the reaction plane in Pb-Pb collisions at sNN=2.76\sqrt{s_{\rm NN}}= 2.76 TeV

Measurements of charge dependent azimuthal correlations with the ALICE detector at the LHC are reported for Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV. Two- and three-particle charge-dependent azimuthal correlations in the pseudo-rapidity range $|\eta| < 0.8$ are presented as a function of the collision centrality, particle separation in pseudo-rapidity, and transverse momentum. A clear signal compatible with a charge-dependent separation relative to the reaction plane is observed, which shows little or no collision energy dependence when compared to measurements at RHIC energies. This provides a new insight for understanding the nature of the charge dependent azimuthal correlations observed at RHIC and LHC energies.Comment: 12 pages, 3 captioned figures, authors from page 2 to 6, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/286

A note on comonotonicity and positivity of the control components of decoupled quadratic FBSDE

In this small note we are concerned with the solution of Forward-Backward Stochastic Differential Equations (FBSDE) with drivers that grow quadratically in the control component (quadratic growth FBSDE or qgFBSDE). The main theorem is a comparison result that allows comparing componentwise the signs of the control processes of two different qgFBSDE. As a byproduct one obtains conditions that allow establishing the positivity of the control process.Comment: accepted for publicatio

Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at sNN\sqrt{s_{NN}} = 5.02 TeV

Two-particle angular correlations between unidentified charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum range 0.7 $< p_{\rm{T}, assoc} < p_{\rm{T}, trig} <$ 5.0 GeV/$c$ is examined, to include correlations induced by jets originating from low momen\-tum-transfer scatterings (minijets). The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range $|\eta|<0.9$. The near-side long-range pseudorapidity correlations observed in high-multiplicity p-Pb collisions are subtracted from both near-side short-range and away-side correlations in order to remove the non-jet-like components. The yields in the jet-like peaks are found to be invariant with event multiplicity with the exception of events with low multiplicity. This invariance is consistent with the particles being produced via the incoherent fragmentation of multiple parton--parton scatterings, while the yield related to the previously observed ridge structures is not jet-related. The number of uncorrelated sources of particle production is found to increase linearly with multiplicity, suggesting no saturation of the number of multi-parton interactions even in the highest multiplicity p-Pb collisions. Further, the number scales in the intermediate multiplicity region with the number of binary nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/161