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Three-jet distributions from weak decay of heavy particles. [Final-state gluon]

Description: Several sources of 3-jet final states produced by the weak decay of mesons containing heavy quarks are examined. Some of the results are applicable to the decay of the W boson into 3 jets. It is found that vector meson 3-jet final states have the same x, spherocity, and thrust distributions as the q anti q g final state of e/sup +/e/sup -/. For pseudoscalar mesons it is found that the 3-jet branching ratio is suppresed by ratios of the final quark masses to the original meson mass. 37 references.
Date: April 1, 1979
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Extended gauge models and e{sup -}e{sup -} {r_arrow} W{sup -}W{sup -} at the NLC

Description: We briefly discuss two possible manifestations of the lepton number violating reaction e{sup -}e{sup -} {r_arrow} W{sub i}{sup -}W{sub j}{sup -}, which probes the masses and mixings of heavy Majorana neutrinos, at the Next Linear Collider (NLC). Cross sections for this process are shown to be potentially quite large at center of mass energies of order 1-1.5 TeV.
Date: October 1, 1995
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Like-sign charged Higgs boson production in e{sup -}e{sup -} collisions at the NLC

Description: We consider the production of a pair of like-sign charged Higgs bosons in e{sup -} e{sup -} collisions at the NLC within the context of several electroweak models with extended symmetry breaking sectors. We find that the rate for this process, which proceeds through W{sup -}W{sup -} fusion, is a very sensitive probe of the nature of these extended Higgs sectors and that the corresponding cross sections can vary by as much as several orders of magnitude at NLC energies.
Date: October 1, 1995
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Extending the kinematic range for W{sub R} searches in e{sup {minus}}e{sup {minus}} collisions at the NLC

Description: While the much discussed lepton-number violating process e{sup {minus}}e{sup {minus}} {yields} W{sub R}{sup {minus}}W{sub R}{sup {minus}} provides an excellent probe of both the Majorana nature of the right-handed neutrino and the symmetry breaking sector of the Left-Right Symmetric Model, it is likely that W{sub R}`s are too massive to be pair produced at the NLC with {radical}s in the 1-1.5 TeV range. The author is thus lead to consider the single W{sub R} production process e{sup {minus}}e{sup {minus}} {yields} W{sub R}{sup {minus}}(W{sub R}{sup {minus}}){sup *} {yields} W{sub R}{sup {minus}} + jj in order to expand the collider`s kinematic reach. After pointing out that W{sub R}`s with masses of order 1 TEV may be missed by future hadron collider searches, the author demonstrates that this three-body process possesses a significant cross section, of order several fb, at the NLC with {radical}s in the range above. The angular distribution of the produced W{sub R}`s is shown to be essentially flat and the potential backgrounds from standard model processes are shown to be small.
Date: July 1, 1994
Creator: Rizzo, T. G.
Partner: UNT Libraries Government Documents Department

Extended gauge sectors

Description: Present and future prospects for the discovery of new gauge bosons, Z{prime} and W{prime}, are reviewed. Particular attention is paid to hadron and e{sup +}e{sup {minus}} collider searches for the W{prime} of the Left-Right Symmetric Model.
Date: February 1, 1995
Creator: Rizzo, T. G.
Partner: UNT Libraries Government Documents Department

Dissecting the Wjj Anomaly: Diagnostic Tests of a Leptophobic Z'

Description: We examine the scenario where a leptophobic Z{prime} boson accounts for the excess of events in the Wjj channel as observed by CDF. We assume generation independent couplings for the Z{prime} and obtain allowed regions for the four hadronic couplings using the measured cross section as well as constraints from dijet production at UA2. These coupling regions translate into well-determined rates for the associated production of Z/{gamma} + Z{prime} at the Tevatron and LHC, as well as W + Z{prime} at the LHC,that are directly correlated with the Wjj rate observed at the Tevatron. The Wjj rate at the LHC is large and this channel should be observed soon once the SM backgrounds are under control. The rates for Z/{gamma} + Z{prime} associated production are smaller, and these processes should not yet have been observed at the Tevatron given the expected SM backgrounds. In addition, we show that more coupling information is obtainable from the M{sub WZ{prime}} distribution. Once detected, these processes will provide further valuable information on the Z{prime} boson couplings.
Date: August 15, 2011
Creator: Hewett, J. L. & Rizzo, T. G.
Partner: UNT Libraries Government Documents Department

Production of heavy squarkonium at the SSC

Description: We study the production of heavy bound states of squarks at the SSC and analyze their decays into longitudinal W's and Z's. In some situations a squarkonium state can be detected through its decay into a pair of W's.
Date: June 1, 1987
Creator: Herrero, M.J.; Mendez, A. & Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

The polarization asymmetry in {gamma}e collisions at the NLC and triple gauge Boson couplings

Description: The capability of the NLC in the {gamma}e collider mode to probe the CP-conserving {gamma}WW and {gamma}ZZ anomalous couplings through the use of the polarization asymmetry is examined. When combined with other measurements, very strong constraints on both varieties of anomalous couplings can be obtained. The author shows that these bounds are complementary to those that can be extracted from data taken at the LHC.
Date: September 1, 1996
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

b {r_arrow} sl{sup +}l{sup {minus}} in the left-right symmetric model

Description: We begin to analyze and contrast the predictions for the decay b {r_arrow} sl{sup +}l{sup {minus}} in the Left-Right Symmetric Model (LMR) with those of the Standard Model (SM). In particular, we show that the forward-backward asymmetry of the lepton spectrum can be used to distinguish the SM from the simplest manifestation of the LRM.
Date: May 1, 1997
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Extended gauge sectors at future colliders: Report of the New Gauge Boson Subgroup

Description: The author summarizes the results of the New Gauge Boson Subgroup on the physics of extended gauge sectors at future colliders as presented at the 1996 Snowmass workshop. He discusses the direct and indirect search reaches for new gauge bosons at both hadron and lepton colliders as well as the ability of such machines to extract detailed information on the couplings of these particles to the fermions and gauge bosons of the Standard Model. 41 refs., 18 figs., 5 tabs.
Date: December 1, 1996
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Constraints on q{bar q}{gamma}{gamma} contact interactions at future hadron colliders

Description: The author explores the capability of the Tevatron and LHC as well as other future hadron colliders to place limits on the possible existence of flavor-independent q{bar q}{gamma}{gamma} contact interactions which can lead to an excess of high p{sub t} diphoton events with large invariant masses. Constraints on the corresponding e{sup +}e{sup {minus}}{gamma}{gamma} contact interaction already exist from LEP. In the case of hadron colliders, strong constraints on the scale associated with such interactions are achievable in all cases, e.g., of order 0.9(3) TeV at TeV33(LHC).
Date: September 1, 1996
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Searches for scalar and vector leptoquarks at future hadron colliders

Description: The search reaches for both scalar(S) and vector(V) leptoquarks at future hadron colliders are summarized. In particular the authors evaluate the production cross sections of both leptoquark types at TeV33 and LHC as well as the proposed 60 and 200 TeV colliders through both quark-antiquark annihilation and gluon-gluon fusion: q{anti q},gg {r_arrow} SS,VV. Experiments at these machines should easily discover such particles if their masses are not in excess of the few TeV range.
Date: September 1, 1996
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Using final state gluons as probes of anomalous top quark couplings at the NLC

Description: The rate and corresponding gluon jet energy distribution for the process e{sup +}e{sup {minus}} {r_arrow} t{anti t}g are sensitive to the presence of anomalous dipole-like couplings of the top to the photon and Z at the production vertex as well as to the gluon itself. For sizeable anomalous couplings substantial derivations in the shape and magnitude of the gluon spectrum from the expectations of the Standard Model are anticipated. The authors explore the capability of the Next Linear Collider to either discover or place bounds on these types of top quark couplings through measurements of the gluon energy distribution. The resulting constraints are found to be quite complementary to those obtained using other techniques.
Date: October 1, 1996
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Searches for new gauge bosons at future colliders

Description: The search reaches for new gauge bosons at future hadron and lepton colliders are summarized for a variety of extended gauge models. Experiments at these energies will vastly improve over present limits and will easily discover a Z` and/or W` in the multi-TeV range.
Date: September 1, 1996
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Constraints on anomalous top quark couplings at the LHC

Description: Measurements of distributions associated with the pair production of top quarks at the LHC can be used to constrain (or observe) the anomalous chromomagnetic dipole moment(k) of the top. For example, using either the tt(bar) invariant mass or the Pt distribution of top we find that sensitivities to ; k; of order 0.05 are obtainable with 100 /fb of integrated luminosity. This is similar in magnitude to what can be obtained at a 500 GeV NLC with an integrated luminosity of 50 /fb through an examination of the e(+)e(-) right arrow tt(bar)g process.
Date: September 1, 1996
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Universality violations at the Z

Description: Universality violations (UV) in the decays of the Z would be a clear signal for new physics beyond the Standard Model (SM). We explore two scenarios which lead to UV in Z decays which may be observable at LEP/SLC and are easily distinguishable from each other. For simplicity, we concentrate on the leptonic decay modes of the Z and discuss present and future limits on these two models. 6 refs., 2 figs.
Date: January 1, 1990
Creator: Rizzo, T. G.
Partner: UNT Libraries Government Documents Department

SUSY Without Prejudice

Description: We begin an exploration of the physics associated with the general CP-conserving MSSM with Minimal Flavor Violation, the pMSSM. The 19 soft SUSY breaking parameters in this scenario are chosen so as to satisfy all existing experimental and theoretical constraints assuming that the WIMP is a thermal relic, i.e., the lightest neutralino. We scan this parameter space twice using both flat and log priors for the soft SUSY breaking mass parameters and compare the results which yield similar conclusions. Detailed constraints from both LEP and the Tevatron searches play a particularly important role in obtaining our final model samples. We find that the pMSSM leads to a much broader set of predictions for the properties of the SUSY partners as well as for a number of experimental observables than those found in any of the conventional SUSY breaking scenarios such as mSUGRA. This set of models can easily lead to atypical expectations for SUSY signals at the LHC.
Date: December 11, 2008
Creator: Berger, C.F.; Gainer, J.S.; Hewett, J.L. & Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Probing the Universal Randall-Sundrum Model at the ILC

Description: The Randall-Sundrum model with all Standard Model (SM) fields in the bulk, including the Higgs, can be probed by precision measurements at the ILC. In particular, the couplings of the Higgs to the gauge bosons of the SM can be determined with high accuracy at the ILC. Here we examine the deviations in these couplings from their SM values within the framework of the Universal Randall-Sundrum Model (URSM) as well as the corresponding couplings of the first Higgs Kaluza-Klein excitation.
Date: December 14, 2005
Creator: Davoudiasl, H.; /Wisconsin U., Madison; Lillie, B.; Rizzo, T.G. & /SLAC
Partner: UNT Libraries Government Documents Department

The effects of detector descoping and neutral boson mixing on new gauge boson physics at the SSC

Description: We examine how the abilities of an SDC-like detector to discover and identify the origin of a new neutral gauge boson are affected by Z{sub 1} {minus} Z{sub 2} mixing and by variations in detector parameters such as lepton pair mass resolution, particle identification efficiency, and rapidity coverage. Also examined is the sensitivity of these results to variations in structure function uncertainties and uncertainties in the machine integrated luminosity. Such considerations are of importance when dealing with the issues of detector descoping and design.
Date: June 1, 1992
Creator: Hewett, J. L. & Rizzo, T. G.
Partner: UNT Libraries Government Documents Department

The LHC Inverse Problem, Supersymmetry and the ILC

Description: We address the question whether the ILC can resolve the LHC Inverse Problem within the framework of the MSSM. We examine 242 points in the MSSM parameter space which were generated at random and were found to give indistinguishable signatures at the LHC. After a realistic simulation including full Standard Model backgrounds and a fast detector simulation, we find that roughly only one third of these scenarios lead to visible signatures of some kind with a significance {ge} 5 at the ILC with {radical}s = 500 GeV. Furthermore, we examine these points in parameter space pairwise and find that only one third of the pairs are distinguishable at the ILC at 5{sigma}.
Date: November 12, 2007
Creator: Berger, C.F.; Gainer, J.S.; Hewett, J.L.; Lillie, B. & Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Higgs Properties in the Fourth Generation MSSM: Boosted Signals Over the 3G Plan

Description: The generalization of the MSSM to the case of four chiral fermion generations (4GMSSM) can lead to significant changes in the phenomenology of the otherwise familiar Higgs sector. In most of the 3GMSSM parameter space, the lighter CP-even h is {approx} 115-125 GeV and mostly Standard Model-like while H,A,H{sup {+-}} are all relatively heavy. Furthermore, the ratio of Higgs vevs, tan {beta}, is relatively unconstrained. In contrast to this, in the 4GMSSM, heavy fourth generation fermion loops drive the masses of h,H,H{sup {+-}} to large values while the CP-odd boson, A, can remain relatively light and tan {beta} is restricted to the range 1/2 {approx}< tan {beta} {approx}< 2 due to perturbativity requirements on Yukawa couplings. We explore this scenario in some detail, concentrating on the collider signatures of the light CP-odd Higgs at both the Tevatron and LHC. We find that while gg {yields} A may lead to a potential signal in the {tau}{sup +}{tau}{sup -} channel at the LHC, A may first be observed in the {gamma}{gamma} channel due to a highly loop-enhanced cross section that can be more than an order of magnitude greater than that of a SM Higgs for A masses of {approx} 115-120 and tan {beta} < 1. We find that the CP-even states h,H are highly mixed and can have atypical branching fractions. Precision electroweak constraints, particularly for the light A parameter space region, are examined in detail.
Date: August 15, 2011
Creator: Cotta, R.C.; Hewett, J.L.; Ismail, A.; Le, M.-P.; Rizzo, T.G. & /SLAC
Partner: UNT Libraries Government Documents Department

Dark Matter in the MSSM

Description: We have recently examined a large number of points in the parameter space of the phenomenological MSSM, the 19-dimensional parameter space of the CP-conserving MSSM with Minimal Flavor Violation. We determined whether each of these points satisfied existing experimental and theoretical constraints. This analysis provides insight into general features of the MSSM without reference to a particular SUSY breaking scenario or any other assumptions at the GUT scale. This study opens up new possibilities for SUSY phenomenology both in colliders and in astrophysical experiments. Here we shall discuss the implications of this analysis relevant to the study of dark matter.
Date: April 7, 2009
Creator: Cotta, R.C.; Gainer, J.S.; Hewett, J.L.; Rizzo, T.G. & /SLAC
Partner: UNT Libraries Government Documents Department