Search for Excess Dimuon Production in the Radial Region (1.6 < r < 10) cm at the D0 Experiment

We report on a study of dimuon events produced in p{bar p} collisions at {radical}s = 1.96 TeV, using 0.9 fb{sup -1} of data recorded by the D0 experiment during 2008. Using information from the inner-layer silicon tracking detector, we observe 712 {+-} 462 {+-} 942 events in which one or both muons are produced in the range 1.6 &lt; r {approx}&lt; 10 cm, which is expressed as a fraction (0.40 {+-} 0.26 {+-} 0.53)% of the total dimuon sample. We therefore see no significant excess of muons produced a few centimeters away from the interaction point

Tevatron Experimental Issues at High Luminosities

In this paper we describe the detector components, triggers and analysis techniques for flavor physics at the Tevatron experiments CDF and D0. As Tevatron performs very well and runs at higher luminosities regularly we also touch issues related to it and efforts to improve detectors and triggers for such running

Observation of Single Top Quark Production at the Tevatron

This paper reports on the first observation of electroweak production of single top quarks by the D0 and CDF collaborations. At Fermilab's 1.96 TeV proton-antiproton collider, a few thousand events are selected from several inverse femtobarns of data that contain an isolated electron or muon and/or missing transverse energy, together with jets that originate from the decays of b quarks. Using sophisticated multivariate analyses to separate signal from background, the D0 collaboration measures a cross section {sigma} (p{bar p} {yields} tb + X, tqb + X) = 3.94 {+-} 0.88 pb (for a top quark mass of 170 GeV) and the CDF collaboration measures a value of 2.3{sub -0.5}{sup +0.6} pb (for a top quark mass of 175 GeV). These values are consistent with theoretical predictions at next-to-leading order precision. Both measurements have a significance of 5.0 standard deviations, meeting the benchmark to be considered unambiguous observation

Combination of CDF and D0 Measurements of the Single Top Production Cross Section

We report a combination of the CDF and D0 measurements of the inclusive single top quark production cross section in the s- and t-channels, {sigma}{sub s+t}, in p{bar p} collisions at a center of mass energy of 1.96 TeV. The total integrated luminosity included in CDF's analysis is 3.2 fb{sup -1} and D0's analysis has 2.3 fb{sup -1}. A Bayesian analysis is used to extract the cross section from the distributions of multivariate discriminants provided by the collaborations. For a top quark mass m{sub t} = 170 GeV/c{sup 2}, we measure a cross section of 2.76{sub -0.47}{sup +0.58} pb. We extract the CKM matrix element |V{sub tb}| = 0.88 {+-} 0.07 with a 95% C.L. lower limit of |V{sub tb}| &gt; 0.77

NLO-QCD Corrections to Dilepton Production in the Randall-Sundrum Model

The dilepton production process at hadron colliders in the Randall-Sundrum (RS) model is studied at next-to-leading order in QCD. The NLO-QCD corrections have been computed for the virtual graviton exchange process in the RS model, in addition to the usual gamma, Z-mediated processes of standard Drell-Yan. K-factors for the cross-sections at the LHC and Tevatron for differential in the invariant mass, Q, and the rapidity, Y, of the lepton pair are presented. We find the K-factors are large over substantial regions of the phase space.Comment: 24 pages, 12 figure

Lepton Polarization Asymmetry in B l l(bar) decays in R-parity violating Minimal Supersymmetric Standard Model

We study the implication of R-parity violating Rp Minimal Supersymmetric Standard Model (MSSM) model in lepton polarization asymmetry ALP in B l l(bar) decays . The analysis show that the ALP is significant in a certain phenomenological parametric region of Yukawa couplings. We have also placed indirect bounds on Lambda' lambda couplings as obtained from B t t(bar).Comment: 6 pages, 4 figures Changes of notation in Eq(8-11,17-19),Eq.20 adde

High Q2Q^2 Physics at HERA and Searches for New Particles

Preliminary results from H1 and ZEUS on Deep Inelastic Scattering (DIS) at high momentum transfer squared $Q^2$ are presented. Used are all available $e^+ p$ data accumulated by the H1 and ZEUS experiments between 1994 and 1997, corresponding to integrated luminosities of $37 {pb}^{-1}$ and $47 {pb}^{-1}$, respectively. The anomalies observed at high $Q^2$ in the 1994 to 1996 data still remain, though with less significance. Since this high $Q^2$ domain represents a new frontier in DIS, the same data are used to search for new particles possessing direct couplings to lepton-quark pairs. Assuming that the slight excess of events observed in Neutral Current DIS is due to a statistical fluctuation, preliminary limits on the production of leptoquarks and of squarks in R-parity violating MSSM are presented.Comment: 14 pages, 12 figures, uses iopart style files, contribution to the 3rd UK Phenomenology Workshop on HERA Physics, Durham, Sep 199

Monte Carlo Exploration of Warped Higgsless Models

We have performed a detailed Monte Carlo exploration of the parameter space for a warped Higgsless model of electroweak symmetry breaking in 5 dimensions. This model is based on the $SU(2)_L\times SU(2)_R\times U(1)_{B-L}$ gauge group in an AdS$_5$ bulk with arbitrary gauge kinetic terms on both the Planck and TeV branes. Constraints arising from precision electroweak measurements and collider data are found to be relatively easy to satisfy. We show, however, that the additional requirement of perturbative unitarity up to the cut-off, $\simeq 10$ TeV, in $W_L^+W_L^-$ elastic scattering in the absence of dangerous tachyons eliminates all models. If successful models of this class exist, they must be highly fine-tuned.Comment: 26 pages, 7 figures; new fig and additional text adde

Rare K and B Decays in the Littlest Higgs Model without T-Parity

We analyze rare K and B decays in the Littlest Higgs (LH) model without T-parity. We find that the final result for the Z^0-penguin contribution contains a divergence that is generated by the one-loop radiative corrections to the currents corresponding to the dynamically broken generators. Including an estimate of these logarithmically enhanced terms, we calculate the branching ratios for the decays K^+ -> pi^+ nu bar nu, K_L -> pi^0 nu bar nu, B_{s,d} -> mu^+ mu^- and B -> X_{s,d} nu bar nu. We find that for the high energy scale f=O(2-3) TeV, as required by the electroweak precision studies, the enhancement of all branching ratios amounts to at most 15% over the SM values. On the technical side we identify a number of errors in the existing Feynman rules in the LH model without T-parity that could have some impact on other analyses present in the literature. Calculating penguin and box diagrams in the unitary gauge, we find divergences in both contributions that are cancelled in the sum except for the divergence mentioned above.Comment: 39 pages, 8 figures, typos corrected, comment on (2.17) and (2.18) added, references added, results unchange