The production of K 0 s, Λs and Λ s has been studied in a 280 GeV muon-proton scattering experiment with almost complete coverage of all kinematic regions. A study is made of the dependence of the multiplicities on the hadronic centre of mass energy, W , and of the Feynman x distributions. It is found that K 0 and Λ production is mostly central and increases strongly with W , whereas Λ production comes mainly from the remnant target system and is only weakly W dependent.
AVERAGE VALUES OF VARIABLES ARE <Q**2>=12GEV**2 , <NU>=76GEV , <W**2>=130GEV**2 , <X BJ>=0.11.
AVERAGE VALUES OF VARIABLES ARE <Q**2>=12GEV**2 , <NU>=76GEV , <W**2>=130GEV**2 , <X BJ>=0.11.
AVERAGE VALUES OF VARIABLES ARE <Q**2>=12GEV**2 , <NU>=76GEV , <W**2>=130GEV**2 , <X BJ>=0.11.
None
Backward Multiplicity.
Forward Multiplicity.
No description provided.
Inclusive production of the Δ (1232) resonance has been measured in 280 GeV/ c muon-proton interactions. The production of the Δ ++ as a function of the variables χ BJ , W , Q 2 , χ F and p T 2 is investigated. The average Δ ++ multiplicity is found to be smaller, by a factor of 6.2 ± 1.2, than the average multiplicity of protons. An upper limit for Δ 0 production is obtained. The net hadronic charge distribution for events with a Δ ++ is presented. The results are compared to the predictions of the Lund and Fire string models.
No description provided.
No description provided.
The photoproduction of $D^{*\pm} (2010)$ mesons associated with a leading neutron has been observed with the ZEUS detector in $ep$ collisions at HERA using an integrated luminosity of 80 pb$^{-1}$. The neutron carries a large fraction, {$x_L>0.2$}, of the incoming proton beam energy and is detected at very small production angles, {$\theta_n<0.8$ mrad}, an indication of peripheral scattering. The $D^*$ meson is centrally produced with pseudorapidity {$|\eta|<1.5$}, and has a transverse momentum {$p_{\it T} > 1.9$ GeV}, which is large compared to the average transverse momentum of the neutron of 0.22 GeV. The ratio of neutron-tagged to inclusive $D^*$ production is $8.85\pm 0.93({\rm stat.})^{+0.48}_{-0.61}({\rm syst.})\%$ in the photon-proton center-of-mass energy range {$130 <W<280$ GeV}. The data suggest that the presence of a hard scale enhances the fraction of events with a leading neutron in the final state.
Integrated cross section. The first DSYS error includes the uncertainty in the luminosity and the second DSYS error is due to the knowledge of the branching ratios.
No description provided.
No description provided.
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.
The XL bins, their acceptance and the acceptance uncertainty. The RH columnshows the contribution from the energy-scale uncertainty - this is completely c orrelated between the bins.
The slope of the PT**2 distribution from the 1995 DIS data. The uncertainties shown in this table were communicated to us by the authors, and supercede those given in the paper.
The normalized cross section (1/SIG)DSIG/dXL for leading neutrons with THETA < 0.8 mrad with statistical errors only.. For the lowest Q**2 data, the normalization uncertainty is +-5 PCT, and with XL > 0.52 there is a further normalization uncertainty of +-4 PCT.. For the intermediate Q**2 and DIS data the normalization uncertainty is +-4 PCT.
None
No description provided.
No description provided.
No description provided.
Hadroproduction of the Jψ and ψ′ states has been studied in 300-GeV/c proton, antiproton, and π±Li interactions. Both total and differential cross sections in xF and pT have been measured for the Jψ for the π±, proton, and antiproton interactions. The ratio of ψ′ to Jψ production has been determined for the four types of beam particles.
No description provided.
No description provided.
No description provided.
We present the xF and pT differential cross sections of J/ψ and ψ′, respectively, in the ranges −0.05<xF<0.25 and pT<3.5 GeV/c. The data samples are constituted by about 12 000 J/ψ and 200 ψ′ produced in proton-silicon interactions at 800 GeV/c and decaying into opposite sign muons. The xF and pT distributions are compared with recent results from experiments E789 at the same energy and to leading order QCD predictions using the MRS D0 parametrization for the parton structure function. The measured shapes of the differential cross sections, except for the dσ/dxF at small xF, agree very well with the prediction, even though their value is quite a bit larger than the prediction. We also present the cosθ differential cross section of the J/ψ which indicates unpolarized production in contrast with color octet models predictions.
Additional systematic error given above.
Additional systematic error given above.
Additional systematic error given above.
The inclusive production of Σ + (1385) and Σ − (1385) has been studied in K − p interactions at 10 and 10 and 16 GeV/ c . It is found that the cross sections for the reactions K − p → Σ ± (1385) + anything are approximately constant in the energy range form 10 to 32 GeV/ c , being ≈ 350 μ b for Σ + (1385) and ≈ 250 μ b for Σ − (1385). The d σ d p ⊥ 2 distributions for Σ ± (1385) fall off exponentially with increasing p ⊥ 2 , with sloped of about 3 (GeV/ c ) −2 . The d σ /d x distributions for Σ + (1385) and Σ − (1385) are markedly different: the production of Σ − (1385) is symmetrical forwards and backwards in the c.m.s.; for Σ + (1385), the distribution is the same as for Σ − (1385) in the forward direction, but presents a large excess of events in the backward direction. This indicates that for the production of both Σ + (1385) and Σ − (1385) the fragmentation of the incoming kaon is negligible. The fragmentation of the target proton is negligible for Σ − (1385), but it is important for Σ + (1385) and is responsible for the excess (∼100 μ b) of its cross section over that for Σ − (1385).
Axis error includes +- 0.0/0.0 contribution (?////RES-DEF(RES=SIG(1385P13) ,BACK=CORRECTED)//CORRECTED FOR UNSEEN DECAY MODES (PDG 1974)).
Axis error includes +- 0.0/0.0 contribution (?////RES-DEF(RES=SIG(1385P13) ,BACK=CORRECTED)//CORRECTED FOR UNSEEN DECAY MODES (PDG 1974)).
Axis error includes +- 0.0/0.0 contribution (?////RES-DEF(RES=SIG(1385P13) ,BACK=CORRECTED)//CORRECTED FOR UNSEEN DECAY MODES (PDG 1974)).
Results are presented on the inclusive π ± production in K − p interactions at 32.1 GeV/ c . The invariant longitudinal distributions have been calculated both for π + and π − in the backward c.m. hemisphere and extrapolated in the forward hemisphere under some physical assumptions. The inclusive cross sections for π + and π − amount to 32.9 ± 1.5 mb and 35.0 ± 0.7 mb respectively. The energy dependence of the inclusive pion production has been analyzed in the framework of Mueller-Regge phenomenology both in the proton fragmentation and in the central region.
No description provided.
No description provided.
No description provided.
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