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J/{sub psi} production: Tevatron and fixed-target collisions

Description: In this talk the author shows the results of a fit of the NRQCD matrix elements to the CDF data for direct J/{psi} production, by including the radiative corrections to the g g {r_arrow} {sup 3} S {sub 1}{sup [1]} channel and the effect of the k{sub T}-smearing. Furthermore he performs the NLO NRQCD analysis of J/{psi} production in fixed-target proton-nucleon collisions and he fits the colour-octet matrix elements to the available experimental data. The results are compared to the Tevatron ones.
Date: June 1, 2000
Creator: Petrelli, A.
Partner: UNT Libraries Government Documents Department

Hard diffraction at CDF

Description: The authors summarize published results on diffractive dijet and W production and review new results on diffractive beauty and J/{psi} production using the rapidity gap method to tag diffraction. The diffractive structure function of the proton obtained from the analysis of dijet events with a leading antiproton is discussed and compared with expectations based on results obtained in deep inelastic scattering experiments at HERA. Also they report on recent results of dijet production in double pomeron exchange.
Date: May 2, 2000
Creator: Solodsky, Andrei
Partner: UNT Libraries Government Documents Department

Onium and b production at the Tevatron

Description: Recent data from the CDF and D0 experiments at the Tevatron are presented on b quark production cross sections, J/{psi}, {psi}{prime} and {Upsilon} production cross sections. An analysis from CDF of the production polarization of the J/{psi}, {psi}{prime} and {Upsilon}(1S) is reviewed and the results discussed in the context of the color octet model.
Date: January 27, 2000
Creator: Sumorok, K.
Partner: UNT Libraries Government Documents Department

Measurement of sin2{beta} from J/{psi} K{sub s} decays

Description: The CP-violating parameter sin 2{beta} is directly measured using 110 pb{sup {minus}1} of data accumulated with the CDF detector at the Fermilab {anti p}p Tevatron collider operating at {radical}s = 1.8 TeV. The signal consists of 395 {+-} 31 B{sub d}{sup 0} {r{underscore}arrow} J/{psi} K{sub s} events. Three tagging methods are used to identify the type of B meson at production (B{sub d}{sup 0} or {anti B}{sub d}{sup 0}). From the CP asymmetry, sin 2{beta} is measured to be 0.79 {sub {minus}0.44}{sup +0.41}, consistent with Standard Model predictions. Sin 2{beta} is in the interval 0 {lt} sin2{beta} {lt} 1 at the 93% confidence level.
Date: January 24, 2000
Creator: Blocker, C.A.
Partner: UNT Libraries Government Documents Department

CDF results on hard diffraction and rapidity gap physics

Description: We review published rapidity gap results on diffractive W and dijet production and discuss new results on diffractive b and J/{psi} production. The diffractive structure function of the proton obtained from Roman pot dijet data is presented and com- pared with expectations based on the diffractive parton densities extracted from DIS at HERA. Also presented are results on dijet production in double Pomeron exchange. Finally, we review hard double-diffractive results (rapidity gaps between jets) and present new results on soft double diffraction.
Date: October 11, 1999
Creator: Convery, M. E.
Partner: UNT Libraries Government Documents Department

Measurements of the CP-violation parameter sin(2 beta) in B{superscipt 0} {right arrow} J/{psi}K{0 over S} decays

Description: In the 110 pb{sup -1} Run I data sample, using three complementary flavor-tagging algorithms CDF has made a new measurement of the CP-violating asymmetry sin(2{beta})=0.79{sup +0.41}{sub -0.44}, This corresponds to the limit sin(2{beta})>-0.08 at 95% confidence level. This result agrees well with predictions from indirect constraints based on fits of elements of the CKM matrix.
Date: May 11, 1999
Creator: Lewis, J. D.
Partner: UNT Libraries Government Documents Department

Search for the B{sub c} meson in hadronic Z{sup 0} decays using the OPAL detector at LEP

Description: A search for decays of the B{sub c} meson was performed using data collected from 1990--1995 with the OPAL detector on or near the Z{sup 0} peak at LEP. The decay channels B{sub c}{sup +} {r_arrow} J/{psi}{pi}{sup +}, B{sub c}{sup +} {r_arrow} J/{psi}a{sub 1}{sup +} and B{sub c}{sup +} {r_arrow} J/{psi}{ell}{sup +}{nu} were investigated, where {ell} denotes an electron or a muon. Two candidates are observed in the mode B{sub c}{sup +} {r_arrow} J/{psi}{pi}{sup +}, with an estimated background of (0.63 {+-} 0.20) events. The weighted mean of the masses of the two candidates is (6.32 {+-} 0.06) GeV/c{sup 2}, which is consistent with the predicted mass of the B{sub c} meson. One candidate event is observed in the mode B{sub c}{sup +} {r_arrow} J/{psi}{ell}{sup +}{nu}, with an estimated background of (0.82 {+-} 0.19) events. No candidate events are observed in the B{sub c}{sup +} {r_arrow} J/{psi}a{sub 1}{sup +} decay mode, with an estimated background of (1.10 {+-} 0.22) events. Upper bounds at the 90% confidence level are set on the production rates for these processes.
Date: January 1, 1999
Creator: Herndon, M.F.
Partner: UNT Libraries Government Documents Department

Vector meson production and nuclear effects in FNAL E866

Description: Fermilab E866/NUSEA is a fixed-target experiment which has made a number of measurements of the production of vector mesons by 800 GeV protons. The nuclear dependence results include measurements for J/{psi}, {psi}{prime} and {phi} production over very broad ranges in {chi}{sub F} and p{sub T}, and the J/{psi} decay angular distribution at very large {chi}{sub F}. Preliminary results from measurements on Be, Fe and W targets are presented and discussed in the context of nuclear effects such as energy loss and multiple scattering of the partons, absorption of the produced c{bar c} pairs, and shadowing. Production mechanisms involving color-singlet or color-octet states for the c{bar c} pair which eventually forms a J/{psi} or {psi}{prime}, have implications on the strength of absorption in the nucleus and on the angular distribution of the decay muons. Their preliminary results on the angular distributions versus {chi}{sub F} and p{sub T} indicate some transverse polarization of the J/{psi} as predicted by models of production through the color octet state. The measurements of dimuons in the 1 to 3 GeV region explore the nuclear dependence of the {phi} meson and also the composition of the continuum between the {phi} and the J/{psi}. These studies of vector meson production and it`s nuclear dependence are critical in furthering the understanding of these processes towards future measurements at RHIC and new results from NA50 at CERN, where J/{psi} suppression is predicted to be an important signature of the creation of quark-gluon plasma in heavy-ion collisions.
Date: December 31, 1998
Creator: Leitch, M.J. & Collaboration, E866 /NUSEA
Partner: UNT Libraries Government Documents Department

Unresolved questions in J/{psi} production and propagation in nuclei

Description: In order to understand the J/{psi} suppression arising from the possible occurrence of the quark-gluon plasma in high-energy heavy-ion collisions, it is necessary to have a comprehensive picture how the J/{psi} and its precursors are produced, what their properties after production are, and how the J/{psi} and its precursors propagate inside nuclear matter. There are unresolved questions in the descriptions of J/{psi} production and propagation. The author outlines some of these questions and discusses the approaches for their resolution.
Date: November 1, 1998
Creator: Wong, C.Y.
Partner: UNT Libraries Government Documents Department

Measurement of B{sup 0}/Bbar{sup 0} {right arrow}J/{psi} K(0 over s) decay asymmetry using same-side b-flavor tagging

Description: We present a measurement of the time-dependent asymmetry in the rate for {anti B}{sup 0} versus B{sup 0} decays to J/{psi}K{sup 0}{sub s}. The data sample consists of 198 {+-} 17 B{sup 0}/{anti B}{sup 0} decays collected by the CDF detector in p{anti p} collisions at the Fermilab Tevatron, where the initial b flavor has been determined by a same-side flavor tagging technique. This asymmetry is interpreted in the Standard Model as a measurement of the CP-violation parameter sin(2{beta}). Our analysis results in sin(2{beta}) = 1:8 {+-} 1:1(stat) {+-} 0:3(syst).
Date: October 1, 1998
Creator: Tseng, J.
Partner: UNT Libraries Government Documents Department

Discovery of the B{sub C} meson

Description: We report on the first observation of the bottom-charm mesons B{sub c} through the decay mode B{sub c}{sup {+-}} {yields} J/{psi}l{sup {+-}}{nu} in 1.8 TeV p{anti p} collisions using the CDF detector at the Fermilab Tevatron. A fit of background and signal contributions to the observed J/{psi}l mass distribution yielded 20.4{sup +6.2}{sub -5.5} events from B{sub c} mesons. A fit to the same distribution with background alone was rejected at the level of 4.8 standard deviations. We measured the B{sub c}{sup +} mass to be 6.40{+-}0.39{+-}0.13 GeV/c{sup 2} and the B{sub c}{sup +} lifetime to be 0.46{sup 0.18}{sub -0.16}(stat.){+-}0.03(syst.) ps. The measured production cross section times branching ratio for B{sub c}{sup +} {yields} J/{psi}l{sup +}{nu} relative to that for B{sup +} {yields} J/{psi}K{sup +} is 0.132{sup 0.041}{sub -0.037}(stat.){+-}0.031(syst.){sup +0.032}{sub -0.020}(lifetime).
Date: July 1, 1998
Creator: Singh, P.P
Partner: UNT Libraries Government Documents Department

Parton Cascade Description of Heavy Ion Collisions at CERN?

Description: There seems to be a general consensus now that a first glimpse of a QGP-like effect has become visible in the beautiful NA50 data on J/{psi} production and the anomalous suppression phenomenon. On the other hand, it is still widely believed that the dynamics of heavy-ion collisions at CERN SPS energy is predominantly governed by soft, non-perturbative physics. This is ironic: after all, it is unlikely that a QGP could be formed if the underlying dynamics were essentially soft, rather than that it requires intense quark-gluon production with sufficient cascade-like reinteractions which drive the matter to large density and equilibrium. Therefore, the author advocates in this contribution that for ultra-relativistic nucleus-nucleus collisions a description based on the pQCD interactions and cascade evolution of involved partons can and should be used, owing to the claim that short-range parton interactions play an important role at sufficiently high beam energies, including CERN energy {radical}s {approx_equal} 20 A GeV. Here mini-jet production which liberates of quarks and gluons cannot be considered as an isolated rare phenomenon, but can occur quite copiously and may lead to complex multiple cascade-type processes.
Date: February 1, 1998
Creator: Geiger, K.
Partner: UNT Libraries Government Documents Department

Ultrarelativistic cascades and strangeness production

Description: A two phase cascade, LUCIFER II, developed for the treatment of ultra high energy Ion-Ion collisions is applied to the production of strangeness at SPS energies. This simulation is able to simultaneously describe both hard processes such as Drell-Yan and slower, soft processes such as the production of light mesons by separating the dynamics into two steps, a fast cascade involving only the nucleons in the original colliding relativistic ions followed, after an appropriate delay, by a normal multiscattering of the resulting excited baryons and mesons produced virtually in the first step. No energy loss can take place in the short time interval over which the first cascade takes place. The chief result is a reconciliation of the important Drell-Yan measurements with the apparent success of standard cascades to describe the nucleon stopping and meson production in heavy ion experiments at the CERN SPS.
Date: February 1998
Creator: Kahana, D. E. & Kahana, S. H.
Partner: UNT Libraries Government Documents Department

Departure from the hadronic scenario at CERN SPS

Description: A review of results from heavy ion experiments at CERN SPS is presented, with an emphasis on the data from Pb induced interactions. Special focus is put on the most significant surprises: anomalous J/{Psi} suppression, change in the spectral shapes of e{sup +}e{sup {minus}} mass distributions in the vector meson domain, and enhanced strange hadron production. Implications of these findings for understanding collision dynamics and, in particular, their role in the search for the new phase of matter, are discussed.
Date: January 1, 1998
Creator: Odyniec, G.
Partner: UNT Libraries Government Documents Department

J/{Psi} suppression as a signal for the quark-gluon plasma

Description: The authors review the search for the quark-gluon plasma using the signal of the suppression of J/{psi} production in high-energy heavy-ion collisions. Recent anomalous J/{psi} suppression in high-energy Pb-Pb collisions observed by the NA50 Collaboration are examined and compared with earlier results from pA and nucleus-nucleus collisions with heavy ions of smaller mass numbers. The anomalous suppression of J/{psi} production in Pb-Pb collisions can be explained as due to the occurrence of a new phase of strong J/{psi} absorption, which sets in when the number of nucleon-nucleon collisions at a spatial point exceeds about 4 and corresponds to a local energy density of about 3.4 GeV/fm{sup 3}.
Date: December 1, 1997
Creator: Wong, C.Y.
Partner: UNT Libraries Government Documents Department

Signatures of Absorption Mechanisms for J{psi} and {psi}` Production in High Energy Heavy-Ion Collisions

Description: J/psi and psi` produced in high-energy heavy-ion collisions are absorbed by their collisions with nucleons and produced soft particles, leading to two distinct absorption mechanisms. The signature of absorption by produced soft particles, as revealed by psi` production data, consists of a gap and a change of the slope in going from the pA line to the nucleus-nucleus line when we make a semi-log plot of the survival probability as a function of the path length. Using this signature, we find from the J/psi production data in pA, O-Cu, O-U, and S-U collisions that the degree of J/psi absorption by produced soft particles is small and cannot account for the J/psi data in Pb-Pb collisions. The anomalous suppression of J/psi production in Pb-Pb collisions can be explained as due to the occurrence of a new phase of strong J/psi absorption, which sets in when the local energy density exceeds about 3.4 GeV/fm3. To probe the chemical content of the new phase, we propose to study the abundance of open-charm mesons and charm hyperons which depends sensitively on the quark chemical potential.
Date: June 1, 1997
Creator: Wong, Cheuk-Yin
Partner: UNT Libraries Government Documents Department

Tests of QCD at HERA: determination of the gluon density

Description: An overview is given of the various methods available to the colliding beam experiments at HERA to determine the gluon density of the proton. The article includes a description of fits to the structure function F{sub 2}, of studies of dijet and open charm production in deep inelastic scattering, of elastic and inelastic {psi} photoproduction, and of inclusive diffractive scattering. 13 refs., 8 figs.
Date: December 31, 1996
Creator: Repond, J.
Partner: UNT Libraries Government Documents Department

D0 papers on B-physics submitted to DPF '96: b-quark inclusive cross sections and b anti-b correlations using dimuons from the D0 experiment; Single muon production in the forward region at [radical]s=1. 8 TEV; Rapidity dependence of the inclusive J[psi] production in the forward region [radical]s=1. 8 TEV; A search for b [r arrow] X[mu][sup +][mu][sup [minus]] and B[sup 0] [r arrow] [mu][sup +][mu][sup [minus]] decays in p anti-p collisions at [radical]s=1. 8 TEV

Description: Paper 1: Using dimuons collected with the D0 detector during the 1993--1995 Tevatron collider run, the authors have measured the b-quark cross section and b[anti b] correlations as given by the difference in azimuthal angle between the two muons. Both measurements agree with the NLO QCD predictions within experimental and theoretical errors. (Three other papers are included in this report.)
Date: November 1, 1996
Creator: Vititoe, D.L. (Arizona Univ., Tucson, AZ (United States). Dept. of Physics); Kozelov, Alexander; Jesik, Richard & Collaboration., D0
Partner: UNT Libraries Government Documents Department

D0 papers on B-physics submitted to DPF '96: b-quark inclusive cross sections and b anti-b correlations using dimuons from the D0 experiment; Single muon production in the forward region at {radical}s=1.8 TEV; Rapidity dependence of the inclusive J{psi} production in the forward region {radical}s=1.8 TEV; A search for b {r_arrow} X{mu}{sup +}{mu}{sup {minus}} and B{sup 0} {r_arrow} {mu}{sup +}{mu}{sup {minus}} decays in p anti-p collisions at {radical}s=1.8 TEV

Description: Paper 1: Using dimuons collected with the D0 detector during the 1993--1995 Tevatron collider run, the authors have measured the b-quark cross section and b{anti b} correlations as given by the difference in azimuthal angle between the two muons. Both measurements agree with the NLO QCD predictions within experimental and theoretical errors. (Three other papers are included in this report.)
Date: November 1996
Creator: Vititoe, D. L.; Kozelov, Alexander; Jesik, Richard & Collaboration, D0
Partner: UNT Libraries Government Documents Department

Fully reconstructed B decay results from CDF

Description: We have measured ratios of branching ratios of {ital B} mesons including charmonium in the final state and use these ratios to derive {ital B} meson branching fractions. Results are also compared to predictions of factorization. We have searched for{ital B}{sup +}{sub {ital c}} {yields} {ital J}/{Psi}{pi}{sup +} and set a limit on {delta}{center_dot}{ital B}. We observe {Lambda}{sub {ital b}} {yields} {ital J}/{Psi}{Lambda} and measure the mass {ital M}({Lambda}{sub {ital b}}) = 5.623{+-} 0.005 {+-} 0.004 GeV/c{sup 2}.
Date: November 1, 1996
Creator: Lewis, J. D.
Partner: UNT Libraries Government Documents Department

J/{psi} and {psi}{prime} suppression by comovers in Pb+Pb collisions

Description: Measurements of {psi} and {psi}{prime} production at the CERN SPS are compared to predictions based on a hadronic model of charmonium suppression. Detailed information is presented to facilitate comparison to other analyses. Sensitivity of these conclusions to model parameters is discussed.
Date: November 1996
Creator: Gavin, S. & Vogt, R.
Partner: UNT Libraries Government Documents Department

Quarkonia production at CDF

Description: In this paper we present results on {ital J}/{Psi}, {Psi}(2{ital S}), {chi}{sub {ital c}} and {Gamma} production at {radical}{ital s} = 1.8 TeV. These results were obtained from data taken with the CDF detector at Fermilab. We cover recently completed analyses of the 1992-1995 collider run. We find an excess of {ital J}/{Psi}, {Psi}(2{ital S}) and {Gamma} production compared with the predictions from the Color Singlet Model. Prospects for the near future are also discussed.
Date: November 1, 1996
Creator: Papadimitriou, V.
Partner: UNT Libraries Government Documents Department

Quarkonium production in proton antiproton collisions at the Tevatron

Description: Charmonium and bottomonium production is studied using {mu}{sup +}{mu}{sup -} data samples collected by the CDF and D{null} experiments during the 1992-96 {ital p{anti p}} collider run at the Fermilab Tevatron. The inclusive cross sections as a function of the transverse momentum of reconstructed quarkonium states are measured. The results are compared with theoretical predictions, which take into account different quarkonium production mechanisms.
Date: November 1, 1996
Creator: Tkaczyk, S.M. & Collaborations, CDF and D0
Partner: UNT Libraries Government Documents Department

Simulation of heavy ion collisions at {radical}s = 20--200 GeV

Description: A new hadronic cascade code (LUCIFER) is introduced, for simulation of relativistic heavy ion collisions at CERN energies and up to RHIC. It is based on a simple, experimentally and theoretically motivated picture of hh interactions. Final state hadrons are produced by decay of intermediate state clusters, or lumps of excited hadronic matter. These are similar to resonances, but have a continuous mass distribution. Clusters are the objects that re-interact in the cascade. Single diffractive dissociation is used to fix the cluster properties. The model has just two parameters: {tau}{sub d}, the decay time of the clusters, and {tau}{sub f} the formation time of the clusters. Comparison is made with recent CERN data in the Pb + Pb system. The first consistent cascade simulation, of J/{psi} production/suppression is presented. It appears likely that a purely hadronic interpretation can be given to recent CERN data on apparently anomalous J/{psi} suppression in Pb + Pb.
Date: November 1, 1996
Creator: Kahana, D.E. & Kahana, S.H.
Partner: UNT Libraries Government Documents Department