Single superpartner production at Tevatron Run II

We study the single productions of supersymmetric particles at Tevatron Run II which occur in the $2 \to 2-body$ processes involving R-parity violating couplings of type \l'_{ijk} L_i Q_j D_k^c. We focus on the single gaugino productions which receive contributions from the resonant slepton productions. We first calculate the amplitudes of the single gaugino productions. Then we perform analyses of the single gaugino productions based on the three charged leptons and like sign dilepton signatures. These analyses allow to probe supersymmetric particles masses beyond the present experimental limits, and many of the \l'_{ijk} coupling constants down to values smaller than the low-energy bounds. Finally, we show that the studies of the single gaugino productions offer the opportunity to reconstruct the $\tilde \chi^0_1$, $\tilde \chi^{\pm}_1$, $\tilde \nu_L$ and $\tilde l^{\pm}_L$ masses with a good accuracy in a model independent way.Comment: 47 pages, epsfi

Soft Gluon Resummation Effects in Single Slepton Production at Hadron Colliders

We investigate QCD effects in the production of a single slepton at hadron colliders in the Minimal Supersymmetric Standard Model without R-parity. We calculate the total cross sections and the transverse momentum distributions at next-to-leading order in QCD. The NLO corrections enhance the total cross sections and decrease the dependence of the total cross sections on the factorization and renormalization scales. For the differential cross sections, we resum all order soft gluon effects to give reliable predictions for the transverse momentum distributions. We also compare two approaches to the non-perturbative parametrization and found that the results are slightly different at the Tevatron and are in good agreement at the LHC. Our results can be useful to the simulation of the events and to the future collider experiments.Comment: 26 pages, 12 figures, RevTeX4; Minor changes; Version to appear in PR

Single superparticle production via γγ\gamma\gamma collision with explicit R-parity violation

We study the single production of scalar neutrinos or charginos via $\gamma\gamma$ collision in an R-parity ($R_{p}$) violating supersymmetric model. It may be possible to detect a sneutrino or a chargino at a Linear Collider (LC) in $\gamma \gamma$ operation mode, as a test of supersymmetry and $R_p$-violation. Because of the clean background in LC, stringent constraints on $R_p$ violating parameters can be obtained even if the process cannot be observed at the future Linear Collider.Comment: 13 pages, 15 figure

New limits on anomalous contributions to the Wtb vertex

The authors would like to thank the Center for Theoretical Physics of the Physics Department at the New York City College of Technology, for providing computing power from their High-Performance Computing Cluster. The work of M.C.N. Fiolhais was supported by FCT Grant No. SFRH/BPD/100379/2014. The work of C. M. Pease was partly supported by Macaulay Honors College. The authors would also like to thank Juan Antonio Aguilar-Saavedra and Nuno F. Castro for a long time collaboration.The latest and most precise top quark measurements at the LHC and Tevatron are used to establish new limits on the Wtb vertex. Recent results on the measurements of the W-boson helicity fractions and single top quark production cross section are combined in order to establish new limits at 95% CL (confidence level). The allowed regions for these limits are presented, for the first time, in three-dimensional graphics, for both real and imaginary components of the different anomalous couplings, providing a new perspective on the impact of the combination of different physics observables. These results are also combined with the prospected future measurement of the single top quark production cross section and W-boson helicity fractions at the LHC.The authors would like to thank the Center for Theoretical Physics of the Physics Department at the New York City College of Technology, for providing computing power from their High-Performance Computing Cluster. The work of M.C.N. Fiolhais was supported by FCT Grant No. SFRH/BPD/100379/2014. TheworkofC.M.PeasewaspartlysupportedbyMacaulay Honors College. The authors would also like to thank Juan Antonio Aguilar-Saavedra and Nuno F. Castro for a long time collaboration

QCD corrections to the production of ttˉγt\bar{t}\gamma at the ILC

A precise calculation of the top quark pair production associated with a hard photon is essential for testing the electroweak property of the top quark in the Standard Model (SM). We investigate the one-loop QCD corrections to the process $e^{+}e^{-} \to t\bar{t}\gamma$ at the International Linear Collider (ILC), and find that the $K$-factor can be as large as 1.238 (1.105, 1.060) for a center-of-mass energy $\sqrt{s}=500 (800, 1500)$ GeV. The transverse momentum distributions of the top quark and photon are respectively shown at leading order (LO) and next-to-leading order(NLO). Due to the asymmetric rapidity distribution of the top (anti-top) quark, we also study the top quark forward-backward asymmetry ($A^{t}_{FB}$) in $t\bar{t}\gamma$ production at NLO, which is found to be 45.82 (55.25, 55.89)% for $\sqrt{s}=500 (800, 1500)$ GeV.Comment: 12 pages, 5 figures, version acceptd by Phys. Lett.

Precision measurements of the top quark mass from the Tevatron in the pre-LHC era

The top quark is the heaviest of the six quarks of the Standard Model. Precise knowledge of its mass is important for imposing constraints on a number of physics processes, including interactions of the as yet unobserved Higgs boson. The Higgs boson is the only missing particle of the Standard Model, central to the electroweak symmetry breaking mechanism and generation of particle masses. In this Review, experimental measurements of the top quark mass accomplished at the Tevatron, a proton-antiproton collider located at the Fermi National Accelerator Laboratory, are described. Topologies of top quark events and methods used to separate signal events from background sources are discussed. Data analysis techniques used to extract information about the top mass value are reviewed. The combination of several most precise measurements performed with the two Tevatron particle detectors, CDF and \D0, yields a value of \Mt = 173.2 \pm 0.9 GeV/$c^2$.Comment: This version contains the most up-to-date top quark mass averag

Top-quark rare decay t→cht\to c h in R-parity-violating SUSY

The flavor-changing top-quark decay $t\to c h$, where $h$ is the lightest CP-even Higgs boson in the minimal supersymmetric standard model, is examined in the R-parity-violating supersymmetric model. Within the existing bounds on the relevant R-parity-violating couplings, the branching fraction for $t\to c h$ can be as large as about $10^{-5}$ in some part of the parameter space.Comment: version to appear in Phys. Lett.