We re-analyze the direct $\jp$ production processes at the Fermilab Tevatron in view of the recent observation at the B-factories, where both $\jp$ inclusive and exclusive production rates are found to be about an order of magnitude larger than the leading order estimates of non-relativistic QCD. The charm quark fragmentation to $\jp$, which is the dominant color-singlet process at high $p_T$, is normalized by the B-factory measurements. The process receives further enhancement due to the charm sea contribution which has so far been ignored in most analyses. After summing up all sub-process contributions, we find that the color-singlet mechanism alone can account for 20% to 90% of the observed direct $\jp$ high $p_T$ production. The polarization rate of the directly produced $\jp$ is sensitive to the fraction of the color-octet contribution, which is employed to fill the gap between the color-singlet prediction and experimental data. With a bigger $K$-factor for the charm quark fragmentation probability, we envisage a smaller matrix element for the color-octet $^3S_1^{(8)}$ state, and this can be examined at the LHC in near future.
The Wjj background has increased by 70%. This decreases the significance of the WH signal somewhat. The significance of the ZH signal remains about the same.
The direct production of $J/ψ(ψ')$ at large transverse momentum, $p_T \gg M_{J/ψ}$, at the Fermilab Tevatron is revisited. It is found that the sea-quark initiated processes dominate in the high-$p_T$ region within the framework of color-singlet model, which is not widely realized. We think this finding is enlightening for further investigation on the charmonium production mechanism.
Preliminary results from a Fermilab study of the sensitivity for higgs production at the Tevatron in run II and beyond are presented. The study extends existing results by systematically combining all decay channels, considering the production of higher mass higgs bosons and interpreting the results in the context of supersymmetric higgs production as well as standard model production. In addition new analysis methods which significantly improve sensisity are used.
The D0 Collaboration has recently reported the measurement of J/ψproduction at low angle. We show here that the inclusion of color octet contributions in any framework is able to reproduce this data.
The merging procedure of tree-level matrix elements with the subsequent parton shower as implemented in SHERPA will be studied for the example of W boson pair production at the Fermilab Tevatron. Comparisons with fixed order calculations at leading and next-to-leading order in the strong coupling constant and with other Monte Carlo simulations validate once more the impact and the quality of the merging algorithm and its implementation.
This letter presents a study of prospects of searching for excited leptons during RunII of the Fermilab Tevatron. We concentrate on single and pair production of excited electrons in the photonic decay channel in one CDF/DO detector equivalent for 2 fb^{-1}. By the end of RunIIa, the limits should be easily extended beyond those set by LEP and HERA for excited leptons with mass above about 190 GeV.
We calculate one-loop corrections to the single-top-quark production via $q\overline{q}' \to t\overline b$ at the Fermilab Tevatron from the Pseudo-Goldstone bosons ( PGBs ) in the framework of one generation technicolor model. The maximum correction to the total cross section for the single-top-quark production is found to reach -2.4% relative to the tree-level cross section, which may be observable at a high-luminosity Tevatron.
We re-examine like-sign dilepton signals at the Fermilab Tevatron assuming that the excess high-$Q^2$ events recently seen at HERA are due to scalar resonances such as squarks of $R$-parity-violating supersymmetry. For gluinos in the mass range of 200--350 GeV, the like-sign dilepton signal can help to make the crucial distinction between the most favoured squark explanation and other proposed solutions.
This dissertation addresses the question of how to detect light top squarks at the upgraded Fermilab Tevatron collider. After a brief introduction to supersymmetry, the basic phenomenology of the light stop is reviewed and the current experimental situation is surveyed. The analysis presented here is based on collider event simulations. The main decay modes accessible to the Tevatron are studied, feasible discovery channels are identified, and recipes for experimental analysis are proposed. It is found that stops with masses up to the top quark mass are liable to detection under these schemes …
In this note we study the prospect of high-precision measurements of W boson mass, top quark mass, and forward-backward asymmetry in Z->ee decays and the search for the Higgs boson during Run 2 to challenge the standard model.
At the Fermilab Tevatron, final states with three tagged b-jets could play an important role in searches for a Higgs boson with mass in the range 100-300 GeV. These signals arise from gb fusion and we demonstrate their observability in the limit of a large b-quark Yukawa coupling. Rather promising discovery limits on such a coupling are obtained and consequent effects on the parameter space of the Higgs-boson sector in the MSSM are discussed.
We have calculated the $O(α_{ew} M_t^2/M_W^2)$ supersymmetric electroweak corrections to single top quark production via $q\bar q' \to t\bar b$ at the Fermilab Tevatron in the minimal supersymmetric model. The supersymmetric electroweak corrections to the cross section are a few percent for $tan β> 1$, and can exceed 10% for $tanβ<1$. The combined effects of SUSY electroweak corrections and the Yukawa corrections can exceed 10% for favorable parameter values, which might be observable at a high-luminosity Tevatron.
We calculate the $O(αm_t^2/m^2_W)$ corrections arising from diagrams involving the top-quark loops to the light neutral Higgs boson production via $q\bar q'\to WH$ at the Fermilab Tevatron in both the standard model and the minimal supersymmetric model. In contrast to the QCD correction which increases the tree-level cross section, the corrections imply a few percent reduction in the production cross section relative to the tree-leve results.
We evaluate the supersymmetric QCD corrections to single top quark production via $q \bar q'\to t \bar b$ at the Fermilab Tevatron in the minimal supersymmetric model. We find that within the allowed range of squark and gluino masses the supersymmetric QCD corrections can enhance the cross section by a few percent. The combined effects of SUSY QCD, SUSY EW, and the Yukawa couplings can exceed 10% for the smallest allowed $\tanβ~ (\simeq 0.25)$ but are only a few percent for $\tanβ>1$.
Four double-parton scattering processes are examined at the Fermilab Tevatron energy. With optimized kinematical cuts and realistic parton level simulation for both signals and backgrounds, we find large samples of four-jet and three-jet+one-photon events with signal to background ratio being 20\%-30\%, and much cleaner signals from two-jet+two-photon and two-jet+$e^+e^-$ final states. The last channel may provide the first unambiguous observation of multiple parton interactions, even with the existing data sample accumulated by the Tevatron collider experiments.
We analyze the prospects of the Tevatron for finding a Higgs boson in the two photon decay mode. We conclude that the Standard Model (SM) Higgs boson will likely not be discovered in this mode. However, we motivate several theories beyond the SM, including the MSSM, that predict a Higgs boson with enhanced branching fractions into photons, and calculate the luminosity needed to discover a general Higgs boson at the Tevatron by a two-photon invariant mass peak at large transverse momentum. We find that a high luminosity Tevatron will play a significant role in discovering or constraining these …
Top quarks can be produced from the electroweak Wtb coupling, leading to a single top or antitop in the final state. We examine single top quark production at the Fermilab Tevatron and calculate the cross section as a function of top quark mass, for each of three separate production processes. We give details of the interferences between Feynman diagrams in W-gluon fusion and then study the effects of an anomalous (V+A) term in the Wtb coupling. Using predictions for the next Tevatron run, we estimate the experimental sensitivity to the CKM matrix element V_tb as a function of the strength of …
The lepton or baryon number violating top quark interactions in the supersymmetric standard model with R parity violation contribute to the process d dbar to t tbar at the tree level via the t- or u-channel sfermion exchange. Since these interactions are chiral, they induce polarization to the top quark in the t tbar events at hadron colliders. We show in this article that the polarization can be a useful observable for probing these interactions at the upgraded Fermilab Tevatron collider, because the polarization is expected to be very small in the standard model.
We calculate the Next-to-Leading Order (NLO) QCD corrections to W-b-bbar production including full bottom-quark mass effects. We study the impact of NLO QCD corrections on the total cross section and invariant mass distribution of the bottom-quark jet pair at the Fermilab Tevatron p-pbar collider. We perform a detailed comparison with a calculation that considers massless bottom quarks. We find that neglecting bottom-quark mass effects overestimates the NLO total cross-section for W-b-bbar production at the Tevatron by about 8% independent of the choice of renormalization and factorization sca…
The application of Neural Networks in High Energy Physics to the separation of signal from background events is studied. A variety of problems usually encountered in this sort of analyses, from variable selection to systematic errors, are presented. The top--quark search is used as an example to illustrate the problems and proposed solutions.
We calculate Yukawa corrections of order $α_{ew} M_t^2/M_W^2$ to single top quark production via $q \bar q'\rightarrow t \bar b$ at the Fermilab Tevatron in the two-Higgs-doublet models. In our calculation we also keep the terms proportional to $ M_b^2 \tan^2 β$ since their effects may become rather important for large $\tanβ$. The corrections can amount to more than a 15\% reduction in the production cross section relative to the tree level result in the general two-Higgs-doublet model, and a 10\% enhancement in the minimal supersymmetric model, which might be observable at a high-luminosity …
The supersymmetric QCD corrections to top quark pair production by $q\bar q$ annihilation in $p\bar p$ collisions are calculated in the minimal supersymmetric model. We consider effects of the mixing of the scalar top quarks on the corrections to the total $t\bar t$ production cross section at the Fermilab Tevatron. We found that such correction is less sensitive to squark mass and gluino mass than in no-mixing case, and in both cases the corrections can exceed 10\% even if we consider the recent CDF limit on squark and gluino masses.
We evaluate the supersymmetric (SUSY) electroweak corrections to the effect of parity nonconservation in $q {\bar q} \to t {\bar t}$ production at the Fermilab Tevatron predicted by the Minimal Supersymmetric Model (MSSM). We find that the parity nonconserving asymmetry from the SUSY electroweak and SUSY Yukawa loop corrections predicted by the minimal supergravity (mSUGRA) model and the MSSM models with scenarios motivated by current data is about one percent. It will be challenging to observe such a small asymmetry at the Tevatron with 10 fb^{-1} of luminosity. It could however be observable…
We propose the measurement of $χ_{cJ}$ polarizations at high energy hadron colliders to study heavy quarkonium production mechanism. We find that the color-singlet model in the $k_t$ factorization approach predicts very different behavior for $χ_{cJ}$ polarizations at the Fermilab Tevatron compared with the NRQCD predictions in the collinear parton model. In the color-singlet $k_t$ factorization approach, for both $χ_{c1}$ and $χ_{c2}$ productions, the helicity $h=0$ states dominate over other helicity states at large $p_T$. These properties are very useful in distinguishing between the two pr…
The electroweak process $p\bar p \to \ell^\pmνγγ$ is calculated at tree level, including finite W width effects. In order to obtain a gauge invariant amplitude, the imaginary parts of $WWγ$ triangle graphs and $WWγγ$ box diagrams have to be included, in addition to resumming the imaginary contributions to the W polarization. We demonstrate the existence of a radiation amplitude zero in $p\bar p \to W^\pm γγ\to \ell^\pmνγγ$, and discuss how it may be observed in correlations of the $γγ$ and lepton rapidities at the Fermilab Tevatron.
Fermiophobic Higgs bosons $h_f$ exhibiting large branching ratios to two photons can arise in models with two or more scalar doublets and/or triplets. In such models the conventional production mechanisms at hadron colliders may be rendered ineffective due to severe mixing angle suppression. In this scenario, double fermiophobic Higgs production may proceed via complementary mechanisms leading to events with up to 4 photons. We perform a simulation of the detection prospects of $h_f$ in the multi-photon (>3) channel at the Fermilab Tevatron and show that a sizeable region of the ($m_{H^\pm},m_…
Associated single top production with a Z boson or a photon at large hadron colliders provides a precise determination of top flavour-changing neutral couplings. The best way to measure these couplings with the up quark at Tevatron is to search for events with three jets and missing energy or events with a photon, a charged lepton, a jet and missing energy. Other decay channels are also discussed.
We calculate the leading electroweak corrections to the light neutral Higgs boson production via $q\bar q'\to WH$ at the Fermilab Tevatron in both the standard model and the minimal supersymmetric model, which arise from the top-quark and Higgs boson loop diagrams. We found that the leading electroweak corrections can exceed the QCD corrections for favorable values of the parameters in the MSSM, but such corrections are only about $-1% \sim -2%$ in the SM, which are much smaller than the QCD corrections. For the mass region of $90 < m_{h_0} < 120$ GeV, the leading electroweak corrections can r…
We perform a Monte-Carlo simulation of scalar leptoquark pair production at the Tevatron (energy =1.8 TeV and luminosity =100 pb^{-1}) with ISAJET. We also investigate the dominant sources of Standard Model background: Z*jj, ZZ production and heavy quark top-antitop. We find that the top-antitop background is the most important except near the Z pole where the Z*jj background is peaked. We also evaluate the signal-to-background ratio and find a discovery reach of 130 GeV (170 GeV) for a branching ratio of B(LQ-> eq)=0.5 (B=1).
We present a calculation of the single top quark cross section for proton-antiproton interactions with sqrt(s) = 1.8 TeV at the Fermilab Tevatron collider. We examine the effects of top mass, parton distribution functions, QCD scale, and collision energy, on each of the component production mechanisms, and study the kinematic distributions for standard model electroweak production. At the upgraded Tevatron with sqrt(s) = 2.0 TeV and high luminosity, it will be possible to test the nature of the Wtb coupling using single top production. We estimate the sensitivity to measure the single top cros…
We examine the experimental observability of the decay mode $t \rightarrow c g$ at the Fermilab Tevatron via the flavor-changing neutral current vertex $t \bar c g$. We find that with the existing data, one should be able to probe the $t \bar c g$ coupling to a value smaller than indirect limits previously obtained from $b\rightarrow s γ$ and the measured branching fraction for $t\rightarrow bW$, reaching $BF(t \rightarrow cg) \sim$ 15\% - 28\%. A data sample of 1~fb$^{-1}$ (10~fb$^{-1}$) at $\sqrt{s}=2$~TeV may probe the $t \rightarrow c g$ branching fraction to a level of 2\% (0.5\%).
If a heavy Dirac monopole exists, the light to light scattering below the monopole production threshold is enhanced due to the strong coupling of monopoles to photons. This effect could be observable in the collision of virtual photons at proton colliders. At the Tevatron it will be seen as pair production of photons with energies 200--400 GeV and roughly compensated transverse momenta 100--400 GeV/c. This effect could be seen at monopole masses about 1--2.5 TeV at the upgraded Tevatron and 7.4--19 TeV at LHC depending on monopole spin.
We investigate the experimental implications of the minimal gauge-mediated low energy supersymmetry breaking (GMLESB) model for Fermilab Tevatron collider experiments. We map out the regions of parameter space of this model that have already been excluded by collider searches and by limits on $b\to sγ$. We use ISAJET to compute the cross sections for a variety of topological signatures which include photons in assocation with multiple leptons, jets and missing transverse energy. The reach in the parameter $Λ$, which fixes the scale of sparticle masses, is estimated to be $\sim 60$, 100 and 135…
We calculate the Next-to-Leading Order (NLO) QCD corrections to Z b anti-b production in hadronic collisions including full bottom-quark mass effects. We present results for the total cross section and the invariant mass distribution of the bottom-quark jet pair at the Fermilab Tevatron p anti-p collider. We perform a detailed comparison with a calculation that considers massless bottom quarks, as implemented in the Monte Carlo program MCFM. We find that neglecting bottom-quark mass effects overestimates the total NLO QCD cross section for Z b anti-b production at the Tevatron by about 7%, ind…
Expecting the forthcoming experiment at the upgraded Fermilab Tevatron, we calculated CP-violating polarization asymmetry of t t-bar, A_{CP}= [sigma(p p-bar --> t(-) t-bar(-) X) - sigma(p p-bar --> t(+) t-bar(+) X)]/ sigma(p p-bar --> t t-bar X), due to possible anomalous chromomagnetic (kappa) and chromoelectric (tilde{kappa}) couplings of the gluon to the top quark. Since kappa and tilde{kappa} are sensitive to a contribution from new physics beyond standard model, this observable is useful to search for a signal of new physics. It was seen that the magnitude of A_{CP} depends only on Im(til…
If next generations of heavy quarks and leptons exist within the standard model (SM), they can manifest themselves in Higgs boson production at the Tevatron and the LHC, before being actually observed. This generation leads to an increase of the Higgs boson production cross section via gluon fusion at hadron colliders by a factor 6-9. So, the study of this process at the Tevatron and LHC can finally fix the number of generations in the SM. Using the $WW^*$ Higgs boson decay channel, the studies at the upgraded Tevatron will answer the question about the next generation for mass values 135 GeV …
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 $WH_{SM} \to \ellνb\bar{b}$ 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 Stan…
In supersymmetric models where the magnitude of the GUT scale gaugino mass parameter M_3 is suppressed relative to M_1 and M_2, the lightest neutralino can be a mixed higgsino-bino state with a thermal relic abundance in agreement with the WMAP central value for Ω_{\rm CDM} h^2 and consistent with all other phenomenological constraints. In these models, the gluino can be as light as 200 GeV without conflicting with the LEP2 bounds on the chargino mass. Thus, gluino pair production can be accessible at the Fermilab Tevatron at high rates. In this framework, gluinos decay radiatively with a larg…
We study the effects of dimension-six operators contributing to the $gt\bar t$ vertex in top quark pair production at the Tevatron collider. We derive both the limits from Run 1 data and the potential bounds from future runs (Run 2 and 3). Although the current constraints are not very strong, the future runs are quite effective in probing these operators. We investigate the possibility of disentangling different operators with the $t\bar t$ invariant mass distribution and the top quark polarization asymmetry. We also study the effects of a different set of operators contributing to single top …
Within a wide class of models, the LEP2 lower limit of 95 GeV on the chargino mass implies gluinos are heavier than $\sim$300 GeV. In this case electroweak $\tw_1\twb_1$ and $\tw_1\tz_2$ production are the dominant SUSY processes at the Tevatron, and the extensively examined isolated trilepton signal from $\tw_1\tz_2$ production assumes an even greater importance. We update our previous calculations of the SUSY reach of luminosity upgrades of the Fermilab Tevatron in this channel incorporating ({\it i}) decay matrix elements in the computation of the momenta of leptons from chargino and neutra…
Recent advances in superconductor properties and superconducting magnet technology have made it possible to build cost-effective, high-performance dipoles with a field of 12 Tesla - 3 times the field strength of the Tevatron. Such magnets could be used to upgrade Fermilab's collider in its existing tunnel to a collision energy $\sqrt s$= 6 TeV and luminosity {$\cal L$}$>$ 10$^{33}$ cm$^{-2}$s$^{-1}$. We have calculated the parton luminosities for quark-antiquark and gluon-gluon scattering for the Tevatron, the Tripler, and LHC. In most models of the Higgs field and supersymmetry, the Tripler w…
The leading weak corrections to the production of top quark pairs via $q\bar{q} \to t\bar{t}$ in $p\bar{p}$ collisions are evaluated. The chromo-anapole form factor of the top quark and effects of parity violation are studied in the Standard Model (SM) and the Minimal Supersymmetric Model (MSSM). The parity violation effect in $q\bar{q} \to g \to t\bar{t}$ from the SM weak corrections is found to be very small. In the MSSM, the effects of parity violation can be enhanced for $\tanβ\equiv v_2/v_1 > \sqrt{m_t/m_b}$.
We consider the hadroproduction of chi_{c1} and chi_{c2} mesons and their subsequent radiative decays to J/psi mesons and photons in the factorization formalism of nonrelativistic quantum chromodynamics, and study the decay angular distributions, by means of helicity density matrices, in view of their sensitivity to color-octet processes. We present numerical results appropriate for the Fermilab Tevatron.
We explore the reach of luminosity upgrades of the Fermilab Tevatron collider for SU(5) supergravity models in which non-universal GUT-scale gaugino masses arise via a vacuum expectation value for the auxiliary component of a superfield that transforms as a 24, 75 or 200 dimensional representation of SU(5). This results in a different pattern of sparticle masses and mixing angles from what is expected in the minimal supergravity model (mSUGRA) with universal GUT scale gaugino masses. We find that the resulting signal cross sections, and hence the reach of the Tevatron, are sensitive to the gau…
We study the most promising signals of Constrained Minimal Supersymmetry detectable at a luminosity upgraded 2 TeV Fermilab Tevatron collider. Using a full event-level Monte Carlo based on Pythia/Jetset, we simulate the trilepton signal examining in detail the effect of constraints on the parameter space. We also simulate the monolepton and dilepton signals, the missing E_T + jets signal, and the signals of stop production in supersymmetry all with full Standard Model backgrounds with realistic detector cuts. We find that large fractions of parameter space can be probed (or eliminated if no si…
The CDF Forward Detector upgrade project was designed to enhance the capabilities for diffractive physics at the Tevatron. It consists of a Roman Pot spectrometer to detect leading antiprotons, a set of counters near and around the beam-pipe to reject the non-diffractive event contamination to the data sample, and two Miniplug calorimeters to measure the event energy flow in the very forward rapidity region. In the novel design of the Miniplugs, a lead/liquid-scintillator is read out by wave-length shifting fibers arranged in a flexible tower geometry and relatively short depth allows calorime…
Because of their Yukawa interactions, third generation squarks may be substantially lighter than those of the first two generations. Assuming that $\tb_1 \to b\tz_1$ and $\tz_1$ escapes experimental detection, we show that experiments at the Main Injector upgrade (integrated luminosity of $2 fb^{-1}$) of the Tevatron should be sensitive to $b$-squark masses up to 210 GeV for $m_{\tz_1} \leq 120$ GeV. For integrated luminosities of $10 fb^{-1}$ (25 $fb^{-1}$) the sbottom mass reach increases by 20 GeV (35 GeV). If the channel $\tb_1 \to b\tz_2$ is also accessible, the reach becomes model-depend…
We estimate the Tevatron Run II potential for top and bottom squark searches. We find an impressive reach in several of the possible discovery channels. We also study some new channels which may arise in non-conventional supersymmetry models. In each case we rely on a detailed Monte Carlo simulation of the collider events and the CDF detector performance in Run I.
We have studied the potential of the CDF and DZero experiments to discover a low-mass Standard Model Higgs boson, during Run II, via the processes $p\bar{p}$ -> WH -> $\ellνb\bar{b}$, $p\bar{p}$ -> ZH -> $\ell^{+}\ell^{-}b\bar{b}$ and $p\bar{p}$ -> ZH ->$ν\barν b\bar{b}$. We show that a multivariate analysis using neural networks, that exploits all the information contained within a set of event variables, leads to a significant reduction, with respect to {\em any} equivalent conventional analysis, in the integrated luminosity required to find a Standard Model Higgs boson in the mass range 90 …
We calculate the three gauge-boson production in the Standard Model at Fermilab Tevatron energies. At $\sqrt s=2$ TeV in $p\bar p$ collisions, the cross sections for the triple gauge-boson production are typically of order 10 femtobarns (fb). For the pure leptonic final states from the gauge-boson decays and with some minimal cuts on final state photons, the cross sections for $p \bar p \rightarrow W^\pm γγ, Zγγ$ and $W^+W^- γ$ processes are of order a few fb, resulting in a few dozen clean leptonic events for an integrated luminosity of 10 fb$^{-1}$. The pure leptonic modes from other gauge-b…
We study the neutral Higgs boson production via the gluon fusion process with the $\tautau$ final state at the upgraded Fermilab Tevatron, including a complete simulation of signal channels and leading background processes. For the SM Higgs boson, this $h\to \tautau$ channel may provide important addition for the Higgs boson discovery in the mass range 120-140 GeV. In minimal supersymmetric models, natural enhancement for the signal rate over the SM expectation makes the $h,H,A\to \tautau$ signal observable for large $\tanβ$ and low $M_A$, which may lead to full coverage for SUSY Higgs paramet…
Top quark pair production at proton-antiproton colliders is known to exhibit a forward-backward asymmetry due to higher-order QCD effects. We explore how this asymmetry might be studied at the Fermilab Tevatron, including how the asymmetry depends on the kinematics of extra hard partons. We consider results for top quark pair events with one and two additional hard jets. We further note that a similar asymmetry, correlated with the presence of jets, arises in specific models for parton showers in Monte Carlo simulations. We conclude that the measurement of this asymmetry at the Tevatron will b…
This paper discusses supersymmetry discovery potential of the upgraded DØexperiment at the Tevatron $p\bar{p}$ collider. Six final states with large transverse energy (momentum) leptons or photons (with or without large transverse momentum imbalances) are studied. These final states are expected to have small backgrounds and are thereby ideal for new physics searches. Implications of the analyses of these final states on Gauge Mediated Supersymmetry Breaking models are discussed for integrated luminosities of 2 and 30 1/fb. This study demonstrates that a large class of supersymmetry models can…
In supersymmetric models with gaugino mediated SUSY breaking (inoMSB), it is assumed that SUSY breaking on a hidden brane is communicated to the visible brane via gauge superfields which propagate in the bulk. This leads to GUT models where the common gaugino mass $m_{1/2}$ is the only soft SUSY breaking term to receive contributions at tree level. To obtain a viable phenomenology, it is assumed that the gaugino mass is induced at some scale $M_c$ beyond the GUT scale, and that additional renormalization group running takes place between $M_c$ and $M_{GUT}$ as in a SUSY GUT. We assume an SU(5)…
We study the observability for a Standard Model-like Higgs boson at an upgraded Tevatron via the modes $p \bar p \to gg \to h \to \ww \to \ljj$ and $\ll$. We find that with c. m. energy of 2 TeV and an integrated luminosity of 30 fb$^{-1}$ the signal may be observable for the mass range of $135 {\gev} \lsim \mh \lsim 180$ GeV at a $3-5σ$ statistical level. We conclude that the upgraded Tevatron may have the potential to detect a SM-like Higgs boson in the mass range from the LEP2 reach to 180 GeV.
We study the inclusive hadrodroduction of D^0, D^+, D^{*+}, and D_s^+ mesons at next-to-leading order in the parton model of quantum chromodynamics endowed with universal non-perturbative fragmentation functions (FFs) fitted to e^+e^- annihilation data from CERN LEP1. Working in the general-mass variable-flavor-number scheme, we resum the large logarithms through the evolution of the FFs and, at the same time, retain the full dependence on the charm-quark mass without additional theoretical assumptions. In this way, the cross section distributions in transverse momentum recently measured by th…
In this work, we present more detail of the calculation on the NLO QCD corrections to polarization of direct J/psi production via color singlet at Tevatron and LHC, as well as the results for Upsilon for the first time. Our results show that the J/psi polarization status drastically changes from transverse polarization dominant at LO into longitudinal polarization dominant in the whole range of the transverse momentum $p_t$ of J/psi when the NLO corrections are counted. For Upsilon production, the p_t distribution of the polarization status behaves almost the same as that for J/psi except that…
In this paper, we study the observability of an invisible Higgs boson at Fermilab Tevatron and CERN LHC through the production channel $ q \bar{q} \to Z H \to \ell^+\ell^-+ \ptmiss $, where $\ptmiss$ is reconstructed from the $\ell^+\ell^-$ with $\ell=e$ or $μ$. A new strategy is proposed to eliminate the largest irreducible background, namely $ q \bar{q} \to Z(\to \ell^+\ell^-) Z(\to ν\barν)$. This strategy utilizes the precise measurements of $ q \bar{q} \to Z(\to \ell^+\ell^-) Z(\to \ell^+\ell^-)$. For $m_H=120$ GeV and with luminosity $30 fb^{-1}$ at Tevatron, a $5σ$ observation of the inv…
The reach of the Fermilab Tevatron for supersymmetric matter has been calculated in the framework of the minimal supergravity model in the clean trilepton channel. Previous analyses of this channel were restricted to scalar masses m_0<= 1 TeV. We extend the analysis to large values of scalar masses m_0\sim 3.5 TeV. This includes the compelling hyperbolic branch/focus point (HB/FP) region, where the superpotential μparameter becomes small. In this region, assuming a 5σ(3σ) signal with 10 (25) fb^{-1} of integrated luminosity, the Tevatron reach in the trilepton channel extends up to m_{1/2}\sim…
An improved understanding of nonperturbative QCD can be obtained by the recently developed soft color interaction models. Their essence is the variation of color string-field topologies, giving a unified description of final states in high energy interactions, e.g., diffractive and nondiffractive events in ep and ppbar. Here we present a detailed study of such models (the soft color interaction model and the generalized area law model) applied to ppbar, considering also the general problem of the underlying event including beam particle remnants. With models tuned to HERA ep data, we find a go…
