Low-Energy Supersymmetry and the Tevatron Bottom-Quark Cross Section

A long-standing discrepancy between the bottom-quark production cross section and predictions of perturbative quantum chromodynamics is addressed. We show that pair production of light gluinos, of mass 12 to 16 GeV, with two-body decays into bottom quarks and light bottom squarks, yields a bottom-quark production rate in agreement with hadron collider data. We examine constraints on this scenario from low-energy data and make predictions that may be tested at the next run of the Fermilab Tevatron Collider.Comment: Version in Phys. Rev. Lett., 4 pp., 1 ps fig., uses RevTeX, added why moderate gluino masses are not ruled out, updated reference

Measurements of the Q2Q^2-Dependence of the Proton and Neutron Spin Structure Functions g1p and g1n

The structure functions g1p and g1n have been measured over the range 0.014 < x < 0.9 and 1 < Q2 < 40 GeV2 using deep-inelastic scattering of 48 GeV longitudinally polarized electrons from polarized protons and deuterons. We find that the Q2 dependence of g1p (g1n) at fixed x is very similar to that of the spin-averaged structure function F1p (F1n). From a NLO QCD fit to all available data we find $\Gamma_1^p - \Gamma_1^n =0.176 \pm 0.003 \pm 0.007$ at Q2=5 GeV2, in agreement with the Bjorken sum rule prediction of 0.182 \pm 0.005.Comment: 17 pages, 3 figures. Submitted to Physics Letters

Nucleon Edm from Atomic Systems and Constraints on Supersymmetry Parameters

The nucleon EDM is shown to be directly related to the EDM of atomic systems. From the observed EDM values of the atomic Hg system, the neutron EDM can be extracted, which gives a very stringent constraint on the supersymmetry parameters. It is also shown that the measurement of Nitrogen and Thallium atomic systems should provide important information on the flavor dependence of the quark EDM. We perform numerical analyses on the EDM of neutron, proton and electron in the minimal supersymmetric standard model with CP-violating phases. We demonstrate that the new limit on the neutron EDM extracted from atomic systems excludes a wide parameter region of supersymmetry breaking masses above 1 TeV, while the old limit excludes only a small mass region below 1 TeV.Comment: 10 pages, 7 figure file

Constraining supersymmetric models from B_d - B-bar_d mixing and the B_d --> J/psi K_S asymmetry

We analyze the chargino contributions to B_d - B-bar_d mixing and CP asymmetry of the B_d --> J/psi K_S decay, in the framework of the mass insertion approximation. We derive model independent bounds on the relevant mass insertions. Moreover, we study these contributions in supersymmetric models with minimal flavor violation, Hermitian flavor structure, and small CP violating phases and universal strength Yukawa couplings. We show that in supersymmetric models with large flavor mixing, the observed values of sin(2 beta) may be entirely due to the chargino-up-squark loops.Comment: 22 pages, 1 figure, minor corrections, version to appear in Phys. Rev.

The Reach of CERN LEP2 and Fermilab Tevatron Upgrades for Higgs Bosons in Supersymmetric Models

Luminosity upgrades of the Fermilab Tevatron pbar-p collider have been shown to allow experimental detection of a Standard Model (SM) Higgs boson up to $m_{H_{SM}}\sim 120$ GeV via $WH_{SM} \to \ell\nu b\bar{b}$ events. This limit nearly saturates the parameter space for many models of weak scale supersymmetry (SUSY) with a minimal particle content. It is therefore interesting to examine the SUSY Higgs reach of future Tevatron experiments. Contours are presented of Higgs boson reach for CERN LEP2 and Tevatron luminosity upgrades for three models of weak scale SUSY: the Minimal Supersymmetric Standard Model (MSSM), the minimal Supergravity model (mSUGRA) and a simple Gauge Mediated SUSY Breaking Model (GMSB). In each case we find a substantial gain in reach at the Tevatron with integrated luminosity increasing from 10 fb^{-1} to 25-30 fb^{-1}. With the larger integrated luminosity, a Higgs search at the Tevatron should be able to probe essentially the entire parameter space of these models. While a discovery would be very exciting, a negative result would severely constrain our ideas about how weak scale supersymmetry is realized.Comment: 12 pages + 7 figures. Uses REVTEX and epsf macros. Several references added, stated value of A-parameters corrected, note added reguarding sgn(mu) dependence in MSSM case. To appear in Physical Review

Measurement of the Proton and Deuteron Spin Structure Functions g2 and Asymmetry A2

We have measured the spin structure functions g2p and g2d and the virtual photon asymmetries A2p and A2d over the kinematic range 0.02 < x < 0.8 and 1.0 < Q^2 < 30(GeV/c)^2 by scattering 38.8 GeV longitudinally polarized electrons from transversely polarized NH3 and 6LiD targets.The absolute value of A2 is significantly smaller than the sqrt{R} positivity limit over the measured range, while g2 is consistent with the twist-2 Wandzura-Wilczek calculation. We obtain results for the twist-3 reduced matrix elements d2p, d2d and d2n. The Burkhardt-Cottingham sum rule integral - int(g2(x)dx) is reported for the range 0.02 < x < 0.8.Comment: 12 pages, 4 figures, 1 tabl

Search for light-to-heavy quark flavor changing neutral currents in νμN\nu _{\mu}N and νˉμN\bar{\nu}_{\mu}N scattering at the Tevatron

We report on a search for flavor-changing neutral-currents (FCNC) in the production of heavy quarks in deep inelastic $\nu_{\mu}N$ and $\bar{\nu}_{\mu}N$ scattering by the NuTeV experiment at the Fermilab Tevatron. This measurement, made possible by the high-purity NuTeV sign-selected beams, probes for FCNC in heavy flavors at the quark level and is uniquely sensitive to neutrino couplings of potential FCNC mediators. All searches are consistent with zero, and limits on the effective mixing strengths $$, $| V_{db}| ^{2}$, and $| V_{sb}| ^{2}$ are obtained

NLO QCD corrections to dijet production via quark contact interactions

We present the exact next-to-leading order (NLO) QCD corrections to dijet production at the LHC via quark contact interactions, with different color and chiral structures induced from new physics. Following the recent analysis of quark compositeness search at the LHC, we find that the NLO QCD corrections can lower the dijet cross sections by several tens percent, depending on the theory parameters and the selected kinematic regions, and reduce the dependence of the cross sections on factorization and renormalization scales. We also calculate the renormalization group (RG) improved NLO cross sections by summing over the large logarithms from the RG running of Wilson coefficients. Moreover, we investigate the NLO QCD effects on various experimental observables and exclusion limits of quark compositeness scale.Comment: minor chang

B -> X_s gamma in Supersymmetry with Explicit CP Violation

We discuss B -> X_s gamma decay in both constrained and unconstrained supersymmetric models with explicit CP violation within the minimal flavor violation scheme by including tan(beta) -enhanced large contributions beyond the leading order. In this analysis, we take into account the relevant cosmological and collider bounds, as well as electric dipole moment constraints. In the unconstrained model, there are portions of the parameter space yielding a large CP asymmetry at leading order (LO). In these regions, we find that the CP phases satisfy certain sum rules, e.g., the sum of the phases of the \mu parameter and the stop trilinear coupling centralize around \pi with a width determined by the experimental bounds. In addition, at large values of tan(beta), the sign of the CP asymmetry tracks the sign of the gluino mass, and the CP asymmetry is significantly larger than the LO prediction. In the constrained minimal supersymmetric standard model based on minimal supergravity, we find that the decay rate is sensitive to the phase of the universal trilinear coupling. This sensitivity decreases at large values of the universal gauino mass. We also show that for a given set of the mass parameters, there exists a threshold value of the phase of the universal trilinear coupling which grows with tan(beta) and beyond which the experimental bounds are satisfied. In both supersymmetric scenarios, the allowed ranges of the CP phases are wide enough to have phenomenological consequences.Comment: 25 pages, 11 figures. Added references, made minor changes in the text; journal versio

Measurement of the ttˉproductioncrosssectionint\bar{t} production cross section in p\bar{p}collisionsat collisions at \sqrt{s}$ = 1.8 TeV

We update the measurement of the top production cross section using the CDF detector at the Fermilab Tevatron. This measurement uses $t\bar{t}$ decays to the final states $e+\nu$+jets and $\mu+\nu$+jets. We search for $b$ quarks from $t$ decays via secondary-vertex identification or the identification of semileptonic decays of the $b$ and cascade $c$ quarks. The background to the $t\bar{t}$ production is determined primarily through a Monte Carlo simulation. However, we calibrate the simulation and evaluate its uncertainty using several independent data samples. For a top mass of 175 $GeV/c^2$, we measure $\sigma_{t\bar{t}}=5.1 \pm 1.5$ pb and $\sigma_{t\bar{t}}=9.2 \pm 4.3$ pb using the secondary vertex and the lepton tagging algorithms, respectively. Finally, we combine these results with those from other $t\bar{t}$ decay channels and obtain $\sigma_{t\bar{t}} = 6.5^{+1.7}_{-1.4}$ pb.Comment: The manuscript consists of 130 pages, 35 figures and 42 tables in RevTex. The manuscript is submitted to Physical Review D. Fixed typo in author lis