Leading neutron production in e+ p collisions at HERA.

The ZEUS collaboration Chekanov, S. ; Krakauer, D. ; Magill, S. ; et al.
Nucl.Phys.B 637 (2002) 3-56, 2002.
Inspire Record 587158 DOI 10.17182/hepdata.46613

The production of neutrons carrying at least 20% of the proton beam energy ($\xl > 0.2$) in $e^+p$ collisions has been studied with the ZEUS detector at HERA for a wide range of $Q^2$, the photon virtuality, from photoproduction to deep inelastic scattering. The neutron-tagged cross section, $e p\to e' X n$, is measured relative to the inclusive cross section, $e p\to e' X$, thereby reducing the systematic uncertainties. For $\xl >$ 0.3, the rate of neutrons in photoproduction is about half of that measured in hadroproduction, which constitutes a clear breaking of factorisation. There is about a 20% rise in the neutron rate between photoproduction and deep inelastic scattering, which may be attributed to absorptive rescattering in the $\gamma p$ system. For $0.64 < \xl < 0.82$, the rate of neutrons is almost independent of the Bjorken scaling variable $x$ and $Q^2$. However, at lower and higher $\xl$ values, there is a clear but weak dependence on these variables, thus demonstrating the breaking of limiting fragmentation. The neutron-tagged structure function, ${{F}^{\rm\tiny LN(3)}_2}(x,Q^2,\xl)$, rises at low values of $x$ in a way similar to that of the inclusive \ff of the proton. The total $\gamma \pi$ cross section and the structure function of the pion, $F^{\pi}_2(x_\pi,Q^2)$ where $x_\pi = x/(1-\xl)$, have been determined using a one-pion-exchange model, up to uncertainties in the normalisation due to the poorly understood pion flux. At fixed $Q^2$, $F^{\pi}_2$ has approximately the same $x$ dependence as $F_2$ of the proton.

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Production of $J/\psi$ in 16-{GeV} and 22-{GeV} $\pi^-$ Cu Collisions

LeBritton, J. ; McCal, D. ; Melissinos, A.C. ; et al.
Phys.Lett.B 81 (1979) 401-404, 1979.
Inspire Record 7053 DOI 10.17182/hepdata.50278

We have measured the inclusive production of J ψ in 16 and 22 GeV π − copper collisions in a wide aperture magnetic spectrometer. The cross section per Cu nucleus for x > 0 corrected for branching ratio is 64 ± 38 nb at 16 GeV and 196 ± 38 nb at 22 GeV. As threshold is approached, the mean values of the Feynman x distribution increase and the cross section for J ψ production drops steeply. This can be understood in terms of the quark-fusion model where the antiquark content of the pion makes an increasingly significant contribution as M 2 s increases.

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Inclusive V0 production cross sections from 920-GeV fixed target proton nucleus collisions.

The HERA-B collaboration Abt, I. ; Abyzov, A. ; Adams, M. ; et al.
Eur.Phys.J.C 29 (2003) 181-190, 2003.
Inspire Record 604661 DOI 10.17182/hepdata.46479

Inclusive differential cross sections $d\sigma_{pA}/dx_F$ and $d\sigma_{pA}/dp_t^2$ for the production of \kzeros, \lambdazero, and \antilambda particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to $\sqrt {s} = 41.6$ GeV in the proton-nucleon system. The ratios of differential cross sections \rklpa and \rllpa are measured to be $6.2\pm 0.5$ and $0.66\pm 0.07$, respectively, for \xf $\approx-0.06$. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions $d\sigma_{pA}/dp_t^2$ also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections $\sigma_{pA}$ on the atomic mass $A$ of the target material is discussed, and the deduced cross sections per nucleon $\sigma_{pN}$ are compared with results obtained at other energies.

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Measurement of J / psi and psi-prime production in 800-GeV/c proton - gold collisions

The E789 collaboration Schub, M.H. ; Jansen, D.M. ; Mishra, C.S. ; et al.
Phys.Rev.D 52 (1995) 1307, 1995.
Inspire Record 394476 DOI 10.17182/hepdata.42428

With a data sample containing 1.1×105 J/ψ→μ+μ− decays reconstructed with 16 MeV/c2 rms mass resolution, we have measured the differential cross sections versus Feynman-x, rapidity, and pT for the production of J/ψ and ψ’ in 800 GeV/c p-Au collisions. Our results are compared with leading-order QCD predictions and with previous measurements. While the shapes of the cross sections are in qualitative agreement with QCD predictions, the magnitudes disagree by factors of 7 (J/ψ) and 25 (ψ’). Assuming an appropriate form for the differential cross sections in regions not measured we derive a total J/ψ production cross section σ(p+N→J/ψ+X)=442±2±88 nb/nucleon and a (model-dependent) total ψ’ cross secton σ(p+N→ψ’+X)=75±5±22 nb/nucleon. For J/ψ produced at central rapidity, dσ(p+N→J/ψ+X)/dy‖y=0=230±5±46 nb/nucleon.

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Production of J / psi and psi (2S) mesons in pi- Be collisions at 515-GeV/c

The E672 & E706 collaborations Gribushin, A. ; Abramov, V. ; Antipov, Yu. ; et al.
Phys.Rev.D 53 (1996) 4723-4733, 1996.
Inspire Record 401108 DOI 10.17182/hepdata.42344

We have studied the production of J/ψ and ψ(2S) charmonium mesons in 515 GeV/c π−Be collisions in the Feynman-x range 0.1<xF<0.8. J/ψ mesons were detected via their decay into μ+μ−, and ψ(2S) mesons were studied in both the μ+μ− and J/ψπ+π− decay modes. J/ψ differential cross sections have been measured as functions of xF,pT2, and the cosine of the Gottfried-Jackson decay angle. We measure an inclusive J/ψ cross section of B(J/ψ→μ+μ−)σ(π−Be→J/ψ+X)/A= [9.3±0.1(stat)±1.1(syst)] nb/nucleon for J/ψ xF≳0.1. Our results are compared with those from other experiments performed at lower beam energies. We also measure the differential ψ(2S) cross section as a function of both xF and pT2, and a ψ(2S) inclusive cross section of B(ψ(2S)→J/ψπ+π−)σ(π−Be→ψ(2S)+X)/A=[7. 4±1.5(stat)±1.2(syst)] nb/nucleon for ψ(2S) xF≳0.1. The fraction of the inclusive J/ψ yield due to ψ(2S) meson decays is 0.083±0.017(stat) ±0.013(syst), and the observed ratio of ψ(2S) decay rates is B(ψ(2S)→J/ψπ+π−)/B(ψ(2S)→μ+μ−) =30.2±7.2(stat)±6.8(syst). We have searched for production of ‘‘hidden’’ charm resonances decaying into either J/ψπ±,ψ(2S)π±, or J/ψπ+π− systems, and report an upper limit of 3.1 nb/nucleon for the product of branching ratio and cross section for the recently reported enhancement at a J/ψπ+π− mass of 3.836 GeV/c2. © 1996 The American Physical Society.

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Properties of $J / \psi$ Production in $\pi^-$ Be and p Be Collisions at 530 GeV/c

The E672/706 collaboration Abramov, V. ; Antipov, Yu. ; Baldin, B. ; et al.
FERMILAB-PUB-91-062-E, 1991.
Inspire Record 315071 DOI 10.17182/hepdata.42566

None

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Neutral strange particle production in K+ and pi+ collisions with Al and Au nuclei at 250-GeV/c

The NA22 collaboration Botterweck, F. ; Charlet, M. ; Chliapnikov, P.V. ; et al.
Z.Phys.C 55 (1992) 373-382, 1992.
Inspire Record 333307 DOI 10.17182/hepdata.14584

Data are presented on inclusiveKs0 and Λ production inK+ and π+ collisions with Al and Au nuclei at 250 GeV/c. Results are given on total inclusive cross sections and theA dependence, as well as on distributions in Feynman-xF, rapidityy and transverse momentum. Ratios ofKS0 and of Λ to π+ production are presented. The data are compared with predictions of the quark-parton model FRITIOF.

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A Search for weakly interacting neutral particles in missing energy events in 450-GeV/c p N collisions

The HELIOS collaboration Åkesson, T. ; Almehed, S. ; Angelis, A.L. S. ; et al.
Z.Phys.C 52 (1991) 219-226, 1991.
Inspire Record 302922 DOI 10.17182/hepdata.15014

We have measured the inclusive cross-section as a function of missing energy, due to the production of neutrinos or new weakly interacting neutral particles in 450 GeV/c proton-nucleus collisions, using calorimetric measurements of visible event energy. Upper limits are placed on the production of new particles as a function of their energy. These upper limits are typically an order

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