共查询到20条相似文献,搜索用时 343 毫秒
1.
Ukegawa F Valls J Vejcik S Velev G Vidal R Vilar R Vologouev I Vucinic D Wagner RG Wagner RL Wahl J Wallace NB Walsh AM Wang C Wang CH Wang MJ Watanabe T Watts T Webb R Wenzel H Wester WC Wicklund AB Wicklund E Williams HH Wilson P Winer BL 《Physical review letters》2000,84(2):232-237
We report a measurement of the fraction of b quarks produced diffractively in &pmacr;p collisions at sqrt[s] = 1.8 TeV. Diffraction is identified by the absence of particles in a forward pseudorapidity region. From events with an electron of transverse momentum 9.5
相似文献
2.
Adler SS Afanasiev S Aidala C Ajitanand NN Akiba Y Al-Jamel A Alexander J Aoki K Aphecetche L Armendariz R Aronson SH Averbeck R Awes TC Babintsev V Baldisseri A Barish KN Barnes PD Bassalleck B Bathe S Batsouli S Baublis V Bauer F Bazilevsky A Belikov S Bjorndal MT Boissevain JG Borel H Brooks ML Brown DS Bruner N Bucher D Buesching H Bumazhnov V Bunce G Burward-Hoy JM Butsyk S Camard X Chand P Chang WC Chernichenko S Chi CY Chiba J Chiu M Choi IJ Choudhury RK Chujo T Cianciolo V Cobigo Y 《Physical review letters》2005,94(8):082302
We report on charged hadron production in deuteron-gold reactions at sqrt[s(NN)]=200 GeV. Our measurements in the deuteron direction cover 1.4相似文献
3.
《The European Physical Journal C - Particles and Fields》2008,55(4):525-538
The effect of the heavy b-quark mass on the two, three and four-jet rates is studied using LEP data collected by the DELPHI
experiment at the Z peak in 1994 and 1995. The rates of b-quark jets and light quark jets (ℓ=uds) in events with n=2, 3, and
4 jets, together with the ratio of two and four-jet rates of b-quarks with respect to light-quarks, Rn
bℓ, have been measured with a double-tag technique using the CAMBRIDGE jet-clustering algorithm. A comparison between experimental
results and theory (matrix element or Monte Carlo event generators such as PYTHIA, HERWIG and ARIADNE) is done after the hadronisation
phase.
Using the four-jet observable R4
bℓ, a measurement of the b-quark mass using massive leading-order calculations gives: This result is compatible with previous three-jet determinations at the MZ energy scale and with low energy mass measurements evolved to the MZ scale using QCD renormalisation group equations. 相似文献
4.
We extend our previous formalism [Phys. Lett.
B 656 45 (2007)] on J/ψ suppression at midrapidity using the colour screening framework. Our formalism is more general as the complete rapidity,
transverse momentum and centrality dependence including J/ψ suppression at forward as well as mid-rapidity can be computed directly from it. We have assumed that QGP fluid is expanding
obeying Bjorken’s boost invariant scaling law and bag model EOS is used. Sequential melting of χ
c
(1P) as well as ψ′ (2S) higher resonances is incorporated. We find that our model shows a reasonable agreement with the mid and forward rapidity
data. Furthermore, we observe a larger suppression at forward rapidity in our model which is again well supported by the PHENIX
data. 相似文献
5.
Jochen Bartels Vittorio Del Duca Mark Wüsthoff 《Zeitschrift fur Physik C Particles and Fields》1997,76(1):75-79
As a signal for the BFKL Pomeron in small-x deep inelastic ep scattering, we calculate the azimuthal dependence of the inclusive cross section of forward jets relative to the outgoing electron. For not very large differences in rapidity between the current jet and the forward jet the cross section peaks at π/2. For increasing rapidity BFKL dynamics predicts a decorrelation in the azimuthal dependence between the electron and the forward jet. 相似文献
6.
P.B. Renton 《The European Physical Journal C - Particles and Fields》1999,8(4):585-591
The couplings of the fermions to the Z boson are of great importance in establishing the validity of the Standard Model and
in looking for physics beyond it. The couplings of the b-quark to the Z boson have been the subject of much experimental study
and theoretical interpretation. The apparent excess in the value of , the ratio of the partial width of the Z boson to to its total hadronic width, above the Standard Model expectation reported a few years ago has now become much less significant.
However, the measurements of the pole forward-backward asymmetry for b-quarks at the Z pole and of the polarisation parameter
, obtained using a polarised electron beam, have improved considerably in accuracy. The latest data are examined and values
of the vector and axial-vector b-quark and c-quark couplings to the Z are extracted. The left and right handed couplings are
also extracted. It is found that whereas the c-quark couplings are compatible with the Standard Model, those of the b-quark
data are only compatible with the Standard Model at about the 1% level. In addition, the individual lepton couplings are extracted
and the degree to which the data support the hypothesis of lepton universality is discussed. The sensitivity of the limits from electroweak fits to the Higgs boson mass to these data is examined.
Received: 21 December 1998 / Revised version: 12 February 1999 / Published online: 15 April 1999 相似文献
7.
The idea of an effective light-particle field theory is used to analyze the effects of heavy quarks in electroproduction. The b-quark distribution is predicted at large Q2 and a systematic treatment of the changing number of quark flavors in a QCD analysis of F2 is presented. 相似文献
8.
9.
Ermias T. Atomssa 《The European Physical Journal C - Particles and Fields》2009,61(4):683-686
Quarkonia suppression is considered to be one of the key probes of the Quark Gluon Plasma (QGP) created in heavy ion collisions.
The PHENIX experiment has measured J/ψ production in a variety of colliding systems. Measurements made in p+p collisions show good agreement with pQCD predictions
and serve as baseline for other systems at the same collision energy. The cold nuclear matter contribution to the suppression
is constrained through measurements in d+Au collisions. In Au+Au, the suppression observed at mid rapidity is smaller than
that at forward rapidity, a tendency opposite to what is expected from the higher gluon density at mid rapidity. The results
will be presented and discussed in this article. 相似文献
10.
Tkaczyk S Tollefson K Tollestrup A Toyoda H Trischuk W de Troconiz JF Tseng J Turini N Ukegawa F Valls J Vejcik S Velev G Vidal R Vilar R Volobouev I Vucinic D Wagner RG Wagner RL Wahl J Wallace NB Walsh AM Wang C Wang CH Wang MJ Watanabe T Waters D 《Physical review letters》2000,84(23):5273-5278
We have searched for direct production of scalar top quarks at the Collider Detector at Fermilab in 88 pb(-1) of p&pmacr; collisions at sqrt[s] = 1.8 TeV. We assume the scalar top quark decays into either a bottom quark and a chargino or a bottom quark, a lepton, and a scalar neutrino. The event signature for both decay scenarios is a lepton, missing transverse energy, and at least two b-quark jets. For a chargino mass of 90 GeV/c(2) and scalar neutrino masses of at least 40 GeV/c(2), we find no evidence for scalar top production and present upper limits on the production cross section in both decay scenarios. 相似文献
11.
Adare A Afanasiev S Aidala C Ajitanand NN Akiba Y Al-Bataineh H Alexander J Angerami A Aoki K Apadula N Aramaki Y Atomssa ET Averbeck R Awes TC Azmoun B Babintsev V Bai M Baksay G Baksay L Barish KN Bassalleck B Basye AT Bathe S Baublis V Baumann C Bazilevsky A Belikov S Belmont R Bennett R Berdnikov A Berdnikov Y Bhom JH Blau DS Bok JS Boyle K Brooks ML Buesching H Bumazhnov V Bunce G Butsyk S Campbell S Caringi A Chen CH Chi CY Chiu M Choi IJ Choi JB Choudhury RK Christiansen P Chujo T 《Physical review letters》2011,107(17):172301
Back-to-back hadron pair yields in d+Au and p+p collisions at √s(NN)=200 GeV were measured with the PHENIX detector at the Relativistic Heavy Ion Collider. Rapidity separated hadron pairs were detected with the trigger hadron at pseudorapidity |η|<0.35 and the associated hadron at forward rapidity (deuteron direction, 3.0<η<3.8). Pairs were also detected with both hadrons measured at forward rapidity; in this case, the yield of back-to-back hadron pairs in d+Au collisions with small impact parameters is observed to be suppressed by a factor of 10 relative to p+p collisions. The kinematics of these pairs is expected to probe partons in the Au nucleus with a low fraction x of the nucleon momenta, where the gluon densities rise sharply. The observed suppression as a function of nuclear thickness, p(T), and η points to cold nuclear matter effects arising at high parton densities. 相似文献
12.
V.A. Khoze M.G. Ryskin W.J. Stirling P.H. Williams 《The European Physical Journal C - Particles and Fields》2003,26(3):429-440
We study central Z-boson production accompanied by rapidity gaps on either side as a way to gauge Higgs weak boson fusion production at the
LHC. We analyse the possible backgrounds for the -decay mode and show that these can be substantially reduced. Special attention is paid to the evaluation of the gap survival
factor, which is the major source of theoretical uncertainty in the rate of H, Z and W central production events with rapidity gaps.
Received: 1 August 2002 / Revised version: 27 September 2002 / Published online: 31 October 2002 相似文献
13.
The energy and centrality independence of the limiting fragmentation for produced mesons have been used to extract the reduced
pseudorapidity (η′ = η − η
beam
) distributions of charged baryons at forward rapidity. The distribution crosses at η′ ≈ = −1 suggesting the prominence of beam protons above that rapidity. The loss of beam rapidity has been extracted which
has been found to increase with centrality. 相似文献
14.
It is shown that the absorption correction due to gluon rescattering changes drastically the value of the cross section for heavy quark production at
and also the ratio of c and b cross sections. The cross section for b-quark production, estimated from the data on muon and J/ψ production should be increased by a factor of about 2–2.5 at Fermilab-Tevatron energies. 相似文献
15.
Rabindra N. Mohapatra 《Physics letters. [Part B]》1979,82(1):101-104
New weak interactions of the b-quark and the τ?-lepton are discussed in a gauge model with exact Cabibbo universality for the light quarks. The model is consistent with all observed neutral current data and leads to new signals in the decay of bb? states to electrons. 相似文献
16.
A kinetic equation approach is applied to model anomalous J/ψ suppression at RHIC and SPS by absorption in a hadron resonance gas which successfully describes statistical hadron production in both experiments. The puzzling rapidity dependence of the PHENIX data is reproduced as a geometric effect due to a longer absorption path for J/ψ production at forward rapidity. 相似文献
17.
P. Aurenche Rahul Basu M. Fontannaz 《The European Physical Journal C - Particles and Fields》2008,57(4):681-688
We discuss, in the framework of perturbative QCD at next to leading order, two related observables which are usually considered
to provide tests of the BFKL dynamics: jet–jet correlations at Tevatron energies and forward particle–jet correlations at
HERA. In the first case we study the rapidity gap dependence of the azimuthal correlations and find slightly too strong correlations
at large gap. In the second case we discuss the cross section as well as the azimuthal correlations over a rapidity gap range
of 5 units. We find that the requirement of a forward particle imposes strong kinematical constraints which distort the distributions,
notably at small rapidity gaps. We also show that the decorrelation is stronger in electroproduction than in hadron–hadron
collisions. Unfortunately data are not yet available for comparison. 相似文献
18.
Adare A Afanasiev S Aidala C Ajitanand NN Akiba Y Al-Bataineh H Alexander J Al-Jamel A Aoki K Aphecetche L Armendariz R Aronson SH Asai J Atomssa ET Averbeck R Awes TC Azmoun B Babintsev V Baksay G Baksay L Baldisseri A Barish KN Barnes PD Bassalleck B Bathe S Batsouli S Baublis V Bauer F Bazilevsky A Belikov S Bennett R Berdnikov Y Bickley AA Bjorndal MT Boissevain JG Borel H Boyle K Brooks ML Brown DS Bucher D Buesching H Bumazhnov V Bunce G Burward-Hoy JM Butsyk S Campbell S Chai JS Chang BS 《Physical review letters》2007,98(23):232301
The PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) has measured J/psi production for rapidities -2.2相似文献
19.
Karl Berkelman 《Physics Reports》1983,98(3):145-187
Present information about the quarkonium system consisting of a b-quark and of its antiquark is reviewed with emphasis on the recent results obtained at the Cornell CESR machine. 相似文献
20.
We show that the ‘orthogonal’ characteristics of the observed rapidity gaps and large forward energy flows in deep inelastic scattering at HERA, can be described within a single framework. Our Monte Carlo model is based on perturbative QCD matrix elements and parton showers together with Lund string model hadronization, but has in addition a new mechanism for soft colour interactions which modifies the perturbative colour structure and thereby the hadronization. Effects of perturbative multiparton emission are investigated and the non-perturbative treatment of the proton remnant is discussed and comparison to the observed transverse energy flow is made. We investigate the resulting diffractive-like properties of the model; such as rapidity gap events, t- and M X -distributions and the diffractive structure function in comparison to H1 data. 相似文献