Single neutral pion production via muon antineutrino charged-current interactions in plastic scintillator (CH) is studied using the \minerva detector exposed to the NuMI low-energy, wideband antineutrino beam at Fermilab. Measurement of this process constrains models of neutral pion production in nuclei, which is important because the neutral-current analog is a background for $\bar{\nu}_e$ appearance oscillation experiments. The differential cross sections for $\pi^0$ momentum and production angle, for events with a single observed $\pi^0$ and no charged pions, are presented and compared to model predictions. These results comprise the first measurement of the $\pi^0$ kinematics for this process.
Flux-averaged differential cross section in $\pi^0$ momentum, $d\sigma/dp_{\pi^0}(10^{-40}\text{cm}^2/\text{nucleon}/(\text{GeV/c})$, for 1$\pi^0$ production with statistical (stat) and systematic (sys) uncertainties.
Flux-averaged differential cross section in $\pi^0$ angle, $d\sigma/d\theta_{\pi^0}(10^{-42}\text{cm}^2/\text{nucleon}/\text{deg.})$, for 1$\pi^0$ production with statistical (stat) and systematic (sys) uncertainties.
Spectra of $K^0_S$ mesons and $\Lambda$ hyperons were measured in p+C interactions at 31 GeV/c with the large acceptance NA61/SHINE spectrometer at the CERN SPS. The data were collected with an isotropic graphite target with a thickness of 4% of a nuclear interaction length. Interaction cross sections, charged pion spectra, and charged kaon spectra were previously measured using the same data set. Results on $K^0_S$ and $\Lambda$ production in p+C interactions serve as reference for the understanding of the enhancement of strangeness production in nucleus-nucleus collisions. Moreover, they provide important input for the improvement of neutrino flux predictions for the T2K long baseline neutrino oscillation experiment in Japan. Inclusive production cross sections for $K^0_S$ and $\Lambda$ are presented as a function of laboratory momentum in intervals of the laboratory polar angle covering the range from 0 up to 240 mrad. The results are compared with predictions of several hadron production models. The $K^0_S$ mean multiplicity in production processes $<n_{K^0_S}>$ and the inclusive cross section for $K^0_S$ production were measured and amount to 0.127 $\pm$ 0.005 (stat) $\pm$ 0.022 (sys) and 29.0 $\pm$ 1.6 (stat) $\pm$ 5.0 (sys) mb, respectively.
$K^0_S$ production cross sections in the [0, 20] mrad polar interval.
$K^0_S$ production cross sections in the [20, 140] mrad polar interval.
$K^0_S$ production cross sections in the [140, 240] mrad polar interval.
The invariant cross section of the reaction of deuteron stripping on carbon target has been measured at a deuteron momentum of 8.9 GeV/c. The cross section is obtained at a zero detection angle of the stripping proton: E/p2xd2σ/dpdΩ=(281+-9)xbxGeV/srx(GeV/c)3. This value is consistent with the one calculated in the framework of the Bertocci-Treleani model of deuteron fragmentation. When the method of Nissen-Meyer is used for orthogonalization of the wave functions of primary deuteron and the (np) system, resulting from its disintegration, a similar calculation gives the result, which is 1.4 times larger than the measured value. Distribution in the cosine of angle of proton yield at the fixed proton momentum p turned out to be near to isotropy one and distribution in p at the fixed cos theta has the maximum at p=50 MeV/c
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The photoproduction process of neutral kaons on a liquid deuterium target is investigated near the threshold region, Egamma = 0.8-1.1 GeV. K0 events are reconstructed from positive and negative pions, and differential cross sections are derived. Experimental momentum spectra are compared with those calculated in the spectator model using a realistic deuteron wave function. Elementary amplitudes as given by recent isobar models and a simple phenomenological model are used to study the effect of the new data on the angular behavior of the elementary cross section. The data favor a backward-peaked angular distribution of the elementary n(gamma,K0)Lambda process, which provides additional constraints on current models of kaon photoproduction. The present study demonstrates that the n(gamma,K0)Lambda reaction can provide key information on the mechanism of the photoproduction of strangeness.
Inclusive momentum spectra for K0 photoproduction.. Data read from plots.
The exclusive production cross sections for $\omega$ and $\phi$ mesons have been measured in proton-proton reactions at $p_{lab}=3.67$ GeV/c. The observed $\phi/\omega$ cross section ratio is $(3.8\pm0.2^{+1.2}_{-0.9})\times 10^{-3}$. After phase space corrections, this ratio is enhanced by about an order of magnitude relative to naive predictions based upon the Okubo-Zweig-Iizuka (OZI) rule, in comparison to an enhancement by a factor $\sim 3$ previously observed at higher beam momenta. The modest increase of this enhancement near the production threshold is compared to the much larger increase of the $\phi/\omega$ ratio observed in specific channels of $\bar pp$ annihilation experiments. Furthermore, differential cross section results are also presented which indicate that although the $\phi$ meson is predominantly produced from a $^3P_1$ proton-proton entrance channel, other partial waves contribute significantly to the production mechanism at this beam momentum.
No description provided.
Differential cross section of OMEGA production.
Differential cross section of PHI production.
The photoproduction of eta-mesons from 2H and 4He has been studied for energies close to the production thresholds. The experiments were carried out with the tagged photon beam of the Mainz MAMI accelerator. The eta-mesons were detected via their two photon decays with the electromagnetic calorimeter TAPS. Total cross sections, angular and momentum distributions of the eta-mesons have been determined for both reactions. The total cross sections in the threshold region show a large enhancement over the predictions of a participant - spectator model, indicating significant final state interaction effects. The results are compared to recent model calculations taking into account nucleon-nucleon and nucleon-eta final state interaction effects on different levels of sophistication.
Total inclusive photoproduction cross sections. Statistical errors only.
Angular distributions of ETA mesons from the Deuterium target in the photon-nucleus cm system. Statistical errors only.
Angular distributions of ETA mesons from the Deuterium target in the photon-nucleus cm system. Statistical errors only.
The ratio of the total exclusive production cross sections for $\eta\prime$ and $\eta$ mesons has been measured in the $pp$ reaction at $p_{beam}=3.67$ GeV/c. The observed $\eta\prime/\eta$ ratio is $(0.83\pm{0.11}^{+0.23}_{-0.18})\times 10^{-2}$ from which the exclusive $\eta\prime$ meson production cross section is determined to be $(1.12\pm{0.15}^{+0.42}_{-0.31})\mu b$. Differential cross section distributions have been measured. Their shape is consistent with isotropic $\eta\prime$ meson production.
No description provided.
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Only statistial errors.
The influence of collision centrality upon spectra of negative particles produced indC, αC and CC interactions at 4.2 GeV/c per nucleon is studied. The netcharge of secondary particles is used as a measure of collision centrality. Comparison with the nucleon-nucleon collisions and with Dubna intranuclear cascade model is presented. The main features of the momentum, rapidity and angular spectra are compatible with the independent, nucleon-nucleon collision picture. Only in thepT spectra, the observed particle excess, for low and highpT, is inconsistent with this approach. In contrast to the pions, the spectra of protons are more sensitive to the collision centrality.
No description provided.
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Using a liquid hydrogen bubble chamber of the ITEP, 80 cm in diameter, a study was made of the 3 H + p → p + n + d reaction with an incident momentum of 5 GeV/c for the tritium nuclei. The reaction cross section was 20.4 ± 0.2 mb. The angular, momentum and mass distributions of the reaction products in the 4π geometry have been obtained. We have separated the phase-space regions corresponding to quasi-free pn scattering and to the final-state Nd interaction. In the region of quasi-free pn scattering various experimental spectra are compared with the theoretical predictions, by using pole diagrams with nuclear vertex functions for three NN potentials: the Yamaguchi potential, the RSC potential and the potential in the quark-compound bag model. In the mass spectra of pn, pd and nd systems no evidence for the exhibition of two- and three-baryon resonances has been obtained.
No description provided.
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BACKGROUND DISTRIBUTION WAS OBTAINED BY USING PROTONS FROM DIFFERENT EVENTS.
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