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Recent results from the search for new phenomena at D0

Description: We present results from several new searches for physics beyond the Standard Model. We describe a search based on the scalar sum of the transverse energy of the event, a global quantity nearly independent of the event topology. We summarize our searches for first generation leptoquarks into all three decay channels, eq{ovr eq}, eq{ovr {nu}q}, and {nu}q{ovr {nu}q} and note that this is the first time that the triumvirate of decay channels has been searched. We do not find any evidence for production of first generation leptoquarks and set a lower limit on the mass of the leptoquark of 175 GeV/c{sup 2} , assuming the decay is exclusively into eq{ovr eq}. We also present results from the first search for a third generation leptoquark with charge {+-}1/3. Again, we find no evidence for its existence for a mass less than 80 GeV/c{sup 2} Finally, we discuss one of our searches for supersymmetry, specifically the pair-production of {tilde e}, {tilde {nu}}, and {tilde {chi}}{sup 0}{sub 2} where the decay yields final states with two photons plus missing transverse energy (E{sub T}). We set limits on the production cross section ranging from 1 pb to 400 fb, depending on the mass. This analysis also sets a model-independent limit of {sigma} {center_dot} B(pp - {gamma}{gamma} {vert_bar} E{sub T} {vert_bar} X) < 185 fb at the 95% CL for E{sub T}{sup ({gamma})} > 12 GeV and {vert_bar}{eta}{vert_bar} < 1.1 T and E{sub T}> 25 GeV.
Date: June 1, 1997
Creator: Wightman, J.A.
Partner: UNT Libraries Government Documents Department

New phenomena searches at the Tevatron

Description: We present here recent searches at the Tevatron for new phenomena. The superlight gravitino, scalar top and scalar bottom quarks searches are described in the framework of the supersymmetric models. We also discuss the new Tevatron limits on the second and third generations leptoquark masses.
Date: May 24, 1999
Creator: Nomerotski, A.
Partner: UNT Libraries Government Documents Department

Search for leptoquarks at d-Zero

Description: We present in this paper the current status of searches for leptoquarks at D0. These results include the use of next leading order theoretical predictions for the cross section for pair production of leptoquarks at hadron colliders. We also present a new optimized analysis for first generation leptoquarks with significant increase in sensitivity relative to earlier searches using DO data. The mass limits derived from this first generation leptoquark search are relevant to the recently reported high mass events at HERA.
Date: June 1, 1997
Creator: Norman, D.M.
Partner: UNT Libraries Government Documents Department

Search for neutral heavy leptons in the NuTeV experiment at Fermilab

Description: Preliminary results are presented from a search for neutral heavy leptons in the NuTeV experiment at Fermilab. The upgraded NuTeV neutrino detector for the 1996-1997 run included an instrumented decay region for the NHL search which, combined with the NuTeV calorimeter, allows detection in several decay modes ({mu}{mu}{nu}, {mu}e{nu}, {mu}{pi}, e{pi}, and ee{nu}). We see no evidence for neutral heavy leptons in our current search in the mass range from 0.3 GeV to 2.0 GeV decaying into final states containing a muon.
Date: December 1, 1998
Creator: Drucker, R.B.
Partner: UNT Libraries Government Documents Department

Searches for new phenomena at the Tevatron: SUSY and technicolor

Description: We present some of the latest updated results on searches for physics beyond the Standard Model at the Tevatron Collider using the full Run 1 data sample of p{anti p} collisions at {radical}s = 1.8 TeV collected with the CDF and D0 detectors. Results are reported relative to searches for squarks and gluinos, scalar top and bottom quarks and superlight gravitino. 95% CL exclusion limits are presented for degenerate states of Technicolor particles {rho}<sub>T</sub> and {omega}<sub>T</sub>.
Date: July 2, 1999
Creator: Rolli, S.
Partner: UNT Libraries Government Documents Department

Technicolor limits at the Tevatron

Description: Direct searches for the technicolor particles at the Tevatron collider experiments at {radical}s=1.8 TeV are described. Various color-singlet and color-octet heavy technimeson states are predicted in the recent technicolor models. The topcolor assisted technicolor model predicts new heavy gluon, top-gluon. These new particles, {rho}{sub T}, {omega}{sub T}, {pi}{sub T}, and top-gluon are expected to be produced in high energy p{anti p} collisions if they exist and they are searched in the world highest energy p{anti p} collider experiments, CDF and D0 experiments. In this report, current mass limits for these particles are shown.
Date: April 19, 1999
Creator: Handa, Takanobu
Partner: UNT Libraries Government Documents Department

Search for new particles in multijet final states at the Tevatron

Description: We present the latest results of the searches for new particles in hadronic final states performed in p{anti p} collisions at {radical}s=1.8 TeV. The large data samples collected with the CDF and D0 detectors at the Tevatron collider between 1992 and 1995 allow searches for low cross section phenomena in dijet and multijet events, despite the hindrance of the high background from normal QCD processes. However no signal for new physics is found, and the data show good agreement with QCD. Limits on the mass and on the cross section of the searched states can thus be set.
Date: August 1, 1997
Creator: Dorigo, T.
Partner: UNT Libraries Government Documents Department

Searches for exotic particles at the Tevatron

Description: This paper reports on recent searches for exotic particles by the CDF and D#31; Collaborations. The results are derived from the data collected during the 1992-95 Run I at the Fermilab Tevatron. Limits are presented on new heavy gauge bosons, leptoquarks, monopoles and technicolor particles.
Date: October 1, 1998
Creator: Grosso-Pilcher, C.
Partner: UNT Libraries Government Documents Department

Supergravity grand unification, proton decay and cosmological constraints

Description: Properties and experimental predictions of a broad class of supergravity grand unified models possessing an SU(5)-type proton decay and R parity are described. Models of this type can be described in terms of four parameters at the Gut scale in addition to those of the Standard Model i.e. m{sub 0} (universal scalar mass), m{sub 1/2} (universal gaugino mass), A{sub 0} (cubic soft breaking parameter) and tan {beta} = <H{sub 2}>/<H{sub 1}>. Thus the 32 SUSY masses can be expressed in terms of m{sub 0}, M{sub 1/2}, A{sub 0} tan {beta} and the as yet unknown t-quark mass M{sub t}. Gut thresholds are examined and a simple model leads to grand unification consistent with p-decay data when 0.114 < {alpha}{sub 3}(M{sub z}) < 0.135, in agreement with current values of {alpha}{sub 3}(M{sub Z}). Proton decay is examined for the superheavy Higgs triplet mass H{sub H3} < 10M{sub G}(M{sub G} {approx_equal} 1.5 {times} 10{sup 16} GeV) and squarks and gluinos lighter than 1 TeV. Throughout most of the parameter space chargino-neutralino scaling relations are predicted to hold: 2m{sub {anti Z}}{sub 1} {congruent} m{sub {anti W}}{sub 1} {congruent} m{sub {anti Z}}{sub 2}, m{sub {anti W}}{sub 1} {approx_equal} (1/4)m{sub {anti g}} (for {mu} > 0) or m{sub {anti W}}{sub 1} {approx_equal} (1/3)m{sub {anti g}} (for {mu} < 0), while m{sub {anti W}}{sub 2} {congruent} m{sub {anti Z}}{sub 3} {congruent} m{sub {anti Z}}{sub 4} {much_gt} m{sub {anti Z}}{sub 1}. Future proton decay experiments combined with LEP2 lead to further predictions, e.g. for the entire parameter space either proton decay should be seen at these or the {anti W}{sub 1} seen at LEP2. Relic density constraints on the {anti Z}{sub 1} further constrain the parameter space e.g. so that m{sub t} < 165 GeV, M{sub h} < 105 GeV, m{sub {anti W}}{sub 1} < 100 GeV ...
Date: May 1, 1995
Creator: Arnowitt, R. & Nath, P.
Partner: UNT Libraries Government Documents Department

Non-SUSY exotic particle searches at the Tevatron

Description: Between 1992 and 1995, the CDF and D0 collaborations collected data from p{anti p} collisions at {radical}s = 1.8 TeV. Recently, several analyses of this data have been performed in search of evidence for various non-Supersymmetric exotic particles. As no evidence for the existence of these particles is observed, confidence level limits are established for exotic particle predictions from various theoretical models. Analyses presented here include searches for Standard Model Higgs, technicolor particles, topcolor-assissted technicolor bosons, and flavor-universal colorons.
Date: June 29, 1999
Creator: Cassada, J.
Partner: UNT Libraries Government Documents Department

Single-top-squark production via baryon-number-violating couplings at the Fermilab Tevatron Collider.

Description: We consider the s-channel R-parity-violating production of a single light top squark {tilde t}{sub 1} and its subsequent R-parity-conserving decay. For masses in the range 180-325 GeV, and R-parity-violating couplings {lambda}{sub 3ij}{double_prime} &gt; 0.02-0.05, we show that discovery of the top squark is possible with 2 fb{sup {minus}1} of integrated luminosity at run II. If no evidence for the top squark is found, the bound on {lambda}{sub 3ij}{double_prime} can be reduced by up to an order of magnitude with existing data from run I, and by two orders of magnitude at run II.
Date: April 29, 1999
Creator: Berger, E. L.; Harris, B. W. & Sullivan, Z.
Partner: UNT Libraries Government Documents Department

New particle searches at the Tevatron (I)

Description: Searches for new particles in p{ovr p} collisions at {radical}s = 1.8 TeV are ongoing at the Fermilab Tevatron collider using the CDF and D0 detectors. Current results from searches for heavy charged vector bosons and fourth generation quarks as well as for Supersymmetric partners of Standard Model quarks and gluons are presented. 11 refs., 4 figs.
Date: May 1, 1996
Creator: Gallas, E.
Partner: UNT Libraries Government Documents Department

Search for squarks and gluinos using dileptons

Description: Gluinos and squarks can be produced in {ital p{anti p}} collisions at {radical}s = 1.8 TeV and decay via charginos and neutralinos to final states containing two (or more) leptons. There is no charge correlation between the leptons of charginos from gluino decays as gluinos are Majorana particles. The strategy of this analysis is to search for an excess of events containing two like-sign isolated leptons, missing energy, and jets. The analysis is based on 81 pb{sup -1} of 1994-5 data recorded at CDF.
Date: October 1, 1996
Creator: Done, J. P.
Partner: UNT Libraries Government Documents Department

Gaugino condensation, loop corrections and S-duality constraint

Description: This talk is a brief review of gaugino condensation in superstring effective field theories and some related issues (such as renormalization of the gauge coupling in the effective supergravity theories and modular anomaly cancellation). As a specific example, we discuss a model containing perturbative (1-loop) corrections to the K{umlt a}hler potential and approximate S-duality symmetry.
Date: November 1, 1996
Creator: Saririan, K.
Partner: UNT Libraries Government Documents Department

Searches with taus at the Tevatron

Description: We discuss tau identification techniques at hadron colliders, and present the measurements and the searches performed so far. We report on top quark pair production in the decay channel containing at least one tau lepton. Also, we present results dedicated to searches for new particles, with taus in the final state. We present a search for the charged Higgs boson in the tau decay channel, as well as for the leptoquark family containing tau leptons. Finally, we indicate the capabilities of detecting and triggering on tau leptons in the future collider run.
Date: April 29, 1999
Creator: Gallinaro, M.
Partner: UNT Libraries Government Documents Department

Search for ZX {yields} {nu}{anti {nu}} b {anti b} Events in the D-Zero Detector

Description: We report on a search for a new particle, X, decaying via X {yields} b{anti b}, made through associated production with a Z boson. We use data collected with the D0 detector operating at the Fermilab Tevatron p{anti p} collider with {radical}s = 1.8 TeV. We utilize muon-tagged jets to identify b-quarks and the {nu}{anti {nu}} channel to detect Z bosons. Preliminary results on cross section limits for X masses between 90 GeV/c{sup 2} and 180 GeV/c{sup 2} are presented.
Date: October 1, 1997
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Searches for new phenomena at CDF

Description: We present recent results of searches for new physics in 110 pb{sup - 1} of p{anti p} collisions at {radical}s = 1800 GeV using the CDF detector. Presented are searches for third generation leptoquarks, charged and neutral Higgs bosons and the supersymmetric partner of the top quark ({tilde t}). A search for new physics in diphoton events tests some models attempting to explain the CDF ``ee{gamma}{gamma}E{sub T}`` event. Finding no signal in any of these channels, production limits are presented.
Date: July 1, 1997
Creator: Wilson, P. J.
Partner: UNT Libraries Government Documents Department

Top quark physics and searches for new phenomena at the Tevatron

Description: The CDF and D0 collaborations each have collected over 110 pb{sup -1} from top quark physics and searches for first generation leptoquarks (LQ), using the entire statistics of these large data sets. After careful selection, both collaborations have collected top quark data samples consisting of several dozen events each. From these events both experiments have measured the top quark mass and pair production cross section in a variety of decay channels, including the so-called dilepton, lepton plus jets, and all jets channels. The combined top quark mass from both experiments in the lepton plus jets channels is m{sub t} = 175.6{+-}5.5 GeV/c{sup 2}. CDF and D0 have also performed optimized searches for the pair production of first generation leptoquarks. No candidate events were found. Combining the results from the ee+jets, e{nu}+jets, and {nu}{nu}+jets channels both experiments set 95% confidence level (CL) upper limits on the LQ pair production cross section as a function of mass and of {beta}, the branching fraction to a charged lepton.
Date: January 1, 1998
Creator: Hall, R.E.
Partner: UNT Libraries Government Documents Department

Search for long-lived charged massive particles at CDF

Description: A search for long-lived charged massive particles in CDF's Run1b data sample is presented. The search looks for highly ionizing tracks which would result from slowly moving massive particles. We search for strongly produced particles using a stable color triplet quark as a reference model, and a separate search was performed for weakly produced particles using long-lived sleptons in Gauge- Mediated Supersymmetry Breaking as a reference model. No excess over background was observed, and we derive limits on the cross-sections for production of these particles. Prospects for RunII are also discussed.
Date: April 16, 1999
Creator: Connolly, Amy
Partner: UNT Libraries Government Documents Department

Discovering technicolor at hadron colliders

Description: Strategies are presented for discovering light, color-singlet technipions ({pi}{sub T}), produced in association with a vector boson through s-channel technirho production, at the Tevatron and LHC. Signal and W+jets background were simulated including detector events. Tagging of b-quarks from the {pi}{sub T} {r_arrow} bb decay is found to be important to reduce the W-jets background. The kinematic properties of signal and background events are significantly different and simple cuts can be used to further improve the signal to background ratio. 4 refs., 5 figs., 1 tab.
Date: June 1, 1996
Creator: Wismersley, J.
Partner: UNT Libraries Government Documents Department

Strong dynamics at the muon collider: Working group report

Description: New strong dynamics at the energy scale {approx} 1 TeV is an attractive and elegant theoretical ansatz for the origin of electroweak symmetry breaking. We review here, the theoretical models for strong dynamics, particularly, technicolor theories and their low energy signatures. We emphasize that the fantastic beam energy resolution ({sigma}{sub E}/E {approximately} 10{sup -4}) expected at the first muon collider ({radical}s=100-500 GeV) allows the possibility of resolving some extraordinarily narrow technihadron resonances and, Higgs-like techniscalars produced in the s-channel. Investigating indirect probes for strong dynamics such as search for muon compositeness, we find that the muon colliders provide unparalleled reaches. A big muon collider ({radical}s=3-4 TeV) would be a remarkable facility to study heavy technicolor particles such as the topcolor Z`, to probe the dynamics underlying fermion masses and mixings and to fully explore the strongly interacting electroweak sector.
Date: March 1, 1998
Creator: Bhat, P. C. & Eichten, E.
Partner: UNT Libraries Government Documents Department

Superheavy dark Matter

Description: If there exists fields of mass of the order of 10{sup 13} GeV and large field inflation occurs, their interaction with classical gravitation will generate enough particles to give the universe critical density today regardless of their nongravitational coupling. In the standard dark matter scenarios, WIMPs are usually considered to have once been in local thermodynamic equilibrium (LTE), and their present abundance is determined by their self-annihilation cross section. In that case, unitarity and the lower bound on the age of the universe constrains the mass of the relic to be less than 500 TeV. On the other hand, if the DM particles never attained LTE in the past, self-annihilation cross section does not determine their abundance. For example, axions, which may never have been in LTE, can have their abundance determined by the dynamics of the phase transition associated with the breaking of U(1){sub PQ}. These nonthermal relics (ones that never obtained LTE) are typically light. However, there are mechanisms that can produce superheavy (many orders of magnitude greater than the weak scale) nonthermal relics. Some of this is reviewed in reference 2. Although not known at the time when this talk was given, it is now known that if the DM fields are coupled to the inflaton field, then the mass of the DM particles that can be naturally produced in significant abundance after inflation can be as large as 10{sup {minus}3} M{sub Pl} (paper in preparation). The author discusses the gravitational production mechanism which is a generic consequence of any large field inflationary phase ending.
Date: May 25, 2000
Creator: Chung, Daniel
Partner: UNT Libraries Government Documents Department