HEPData Search

If quarks are composite particles then excited states are expected. We have searched in pp¯ collisions for excited quarks (q*) which decay to common quarks by emitting a W boson (q*→qW) or a photon (q*→qγ). The simplest model of excited quarks has been excluded for mass M*<540 GeV/c2 at 95% confidence level.

3 data tables

Table 1

No description provided.

Table 2

No description provided.

Table 3

No description provided.

First results of the CERES electron pair spectrometer from p + Be, P + Au and S + Au collisions

The CERES/NA45 collaboration Drees, A. ; Baur, R. ; Breskin, A. ; et al.

Nucl.Phys.A 566 (1994) 87C-94C, 1994.

Inspire Record 362492 DOI 10.17182/hepdata.8728

The CERES experiment (CErenkov Ring Electron Spectrometer) studies the production of low mass e + e − pairs in proton-proton, proton-nucleus and nucleus-nucleus interactions at the CERN SPS. The CERES spectrometer, has a novel design based on two Ring Imaging Cherenkov (RICH) counters, and it operates close to its design specifications. Data were recorded with 200 GeV u sulfur beam and 450 GeV proton beam. The analysis is in progress. We have extracted first e + − -pairs samples for p+Be, p+Au and S+Au collisions. In addition other physics topics were addressed. Inclusive photon spectra were measured in S+Au interactions. No excess over known hadronic sources was found within our present systematic error of 11%. Results on high p i charged pion spectra are presented up to 4 GeV c . We also studied the production of e + e − -pairs m the strong electromagnetic fields of very peripheral S+Pt collisions. The data are well described by a first-order perturbative QED-calculation.

2 data tables

Table 1

NON-DISRUPTIVE S+PT COLLISIONS.

Table 2

No description provided.

Scaling violations of the proton structure function f2 at small x

The H1 collaboration Abt, I. ; Ahmed, T. ; Andreev, V. ; et al.

Phys.Lett.B 321 (1994) 161-167, 1994.

Inspire Record 360235 DOI 10.17182/hepdata.45140

An analysis is presented of scaling violations of the proton structure function F 2 ( x , Q 2 ) measured with the H1 detector at HERA in the range of Bjorken x values between x = 3 × 10 −4 and 10 −2 for four-momentum transfers Q > 2 larger than 8.7 GeV 2 . The structure function F 2 ( x , Q 2 ) is observed to rise linearly with ln Q 2 . Under the assumption that the observed scaling violations at small x ⩽ 0.01 are described correctly by perturbative QCD, an estimate is obtained of the gluon distribution function G ( x , Q 0 2 ) at Q 2 2 = 20 GeV 2 .

1 data table

Table 1

No description provided.

Production of J / psi at large x(F) in 800-GeV/c p copper and p beryllium collisions

Kowitt, M.S. ; Gidal, G. ; Ho, P.M. ; et al.

Phys.Rev.Lett. 72 (1994) 1318-1321, 1994.

Inspire Record 361036 DOI 10.17182/hepdata.42472

The differential cross sections dσ/dxF for J/ψ produced inclusively in 800 GeV/c p-Cu and p-Be collisions have been measured in the kinematic range 0.30≤xF≤0.95 through the decay mode J/ψ→μ+μ−. They are compared with the predictions of the semilocal duality model for several sets of parton density functions. No evidence for a suggested intrinsic charm contribution to the cross section is observed. The ratio of the differential cross sections for Cu and Be targets confirms the suppression of J/ψ production in heavy nuclei at large xF.

2 data tables

Table 1

No description provided.

Table 2

No description provided.

Massive hadron pair production by 800-geV/c protons on nuclear targets

White, H.B. ; Turner, Kathleen R. ; Boca, G. ; et al.

Phys.Rev.D 48 (1993) 3996-4006, 1993.

Inspire Record 359158 DOI 10.17182/hepdata.22668

We report data on proton-nucleon collisions obtained on Fermilab experiment E711, in which high transverse momentum hadrons are produced near 90° in the proton-nucleon center of mass forming high mass states, using an 800 GeV/c proton beam on targets of beryllium, aluminum, iron, and tungsten. The data presented cover the mass range from 7 to 15 GeV/c2, the three dihadron charge states ++, +-, and --, and parton-parton scattering angles up to cosθ*=0.50. We present the differential mass dihadron cross section, as well as the angular and charge dependence of the measurement. The cross section as a function of the parton-parton scattering angle for the three charge states is shown to vary linearly with the value of the atomic weight. While the angular distributions are shown to be independent of the target type, a small dependence on the charge state of the distributions is observed. The data are shown to be in good agreement with extrapolations from previous measurements and phenomenological QCD calculations.

4 data tables

Table 1

Atomic weight dependence as function of the parton-parton scattering angle. This angle (theta cm) is defined as the polar angle between the dihadron axis and the beam director in the rest frame of the massive dihadron state. Cross section parameterised as SIG0(MASS**A). Measurements of A are presented here as POWER(N=A,YN=SIG).

Table 2

Table 3

Errors are statistical only.

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rivet Analysis
Production of Lambda and Lambda anti-Lambda correlations in the hadronic decays of the Z0

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adye, T. ; et al.

Phys.Lett.B 318 (1993) 249-262, 1993.

Inspire Record 360638 DOI 10.17182/hepdata.48369

An analysis of the production of the Λ baryon in the hadronic decays of the Z 0 is presented, based on about 993K multihadronic events collected by the DELPHI detector at LEP during 1991 and 1992. The differencial cross section of the Λ and the correlations between Λ and Λ produced in the same event are compared to current models, based both on string fragmentation and on cluster decay. The predictions of the string fragmentation model are found to give satisfactory agreements with the data, clearly better than those of the cluster model.

6 data tables

Table 1

No description provided.

Table 2

Combined LAMBDA and LAMBDABAR multiplicity.

Table 3

Errors contain systematic uncertainties.

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rivet Analysis
Measurement of two photon production of the chi(c2)

The CLEO collaboration Shelkov, V. ; Dominick, J. ; Sanghera, S. ; et al.

Phys.Rev.D 50 (1994) 4265-4271, 1994.

Inspire Record 359316 DOI 10.17182/hepdata.52343

The CLEO II detector is used to search for the production of χc2 states in two-photon interactions. We use the signature χc2→γJ/ψ→γl+l− with l=e,μ. Using 1.49 fb−1 of data taken with beam energies near 5.29 GeV, the two-photon width of the χc2 is determined to be Γ(χc2→γγ)=1.08±0.30(stat)±0.26(syst) keV, in agreement with predictions from perturbative QCD.

2 data tables

Table 1

Results below were obtained usign J/psi from-factors in the two photon propogators, and assumes that only transversely polarized photons are significant inthe production of the CHI/C2(1P) state.

Table 2

No description provided.

Measurement of b anti-b correlations at the CERN p anti-p collider

The UA1 collaboration Albajar, C. ; Ankoviak, K. ; Bartha, S. ; et al.

Z.Phys.C 61 (1994) 41-52, 1994.

Inspire Record 359461 DOI 10.17182/hepdata.14368

We report on measurements of correlated$b\bar b$ production in$p\bar p$ collisions at$\sqrt s = 630GeV$, using dimuon data to tag both theb and$\bar b$ quarks. Starting from an inclusive dimuon sample we obtain improved cross-sections for single inclusive beauty production and confirm our earlier results on$B^0 - \bar B^0$ mixing. From a study of$b\bar b$ correlations we derive explicit cross-sections for semi-differential$b\bar b$ production. We compare the measured cross-sections and correlations to$\mathcal{O}\left( {\alpha _s^3 } \right)$ QCD predictions and find good quantitative agreement. From the measured angular distributions we establish a size-able contribution from higher order QCD processes with a significance of about seven standard deviations. A large nonperturbative contribution to these higher order corrections is excluded.

17 data tables

Table 1

The first error is PT-dependent, and the second is PT-independent. Dimuons from different b-quarks.

Table 2

The first error is PT-dependent, and the second is PT-independent. Dimuons from b chain decays (b --> c + mu, c --> mu).

Table 3

Total cross-section for single b-quark production in the restricted rapidity range.

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Production of charmed mesons in Z decays

Single photon and neutral meson production from WA80

Search for excited quarks in p anti-p collisions at s**(1/2) = 1.8-TeV

First results of the CERES electron pair spectrometer from p + Be, P + Au and S + Au collisions

Scaling violations of the proton structure function f2 at small x

Production of J / psi at large x(F) in 800-GeV/c p copper and p beryllium collisions

Massive hadron pair production by 800-geV/c protons on nuclear targets

rivet Analysis
Production of Lambda and Lambda anti-Lambda correlations in the hadronic decays of the Z0

rivet Analysis
Measurement of two photon production of the chi(c2)

Measurement of b anti-b correlations at the CERN p anti-p collider