Results are presented on effective-mass distributions, differentisl cross sections and longitudinal c.m. momentum distributions for the channels K − p → K − p π o , K o p π − and K − π + n , obtained from a sample of approximately 28 000 inelastic two-pronged interactions at 4.2 GeV/ c incident momentum. The results are in satisfactory agreement with the prediction of a generalized Veneziano-model corrected for (non-dual) π -and pomeron exchange. For the channel K − pπ o pomeron exchange contributes about 20% of the cross section. In the channel K − π + n the dual, pion and pomeron contributions are responsible for resp. 15%, 65% and 20% of the total cross section.
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A bubble-chamber study is presented of a 10 events/μb experiment using K − mesons of 4.25 GeV/ c incident momentum. Differential and total cross sections are determined for 7 different reactions: K − p → K 0 n ( la ), → π 0 Λ ( lb ), → ηΛ ( lc ), → η′Λ ( ld ), → π − Σ ( le ), → π + Σ − ( lf ), K + Ξ − ( lg ) . The experimental characteristics in d σ /d t of each reaction are described: (la) shows a levelling off at t = 0 (GeV/ c ) 2 , a break at t = −0.6 (GeV/ c ) 2 and no backward events, (lb) d σ /d t has a smooth behaviour and a measurable backward component with an indication of a dip at u = −0.2 (GeV/ c ) 2 , (1c) d σ /d t shows a dip in the region between t ≈ −0.2 and −0.4 (GeV/ c ) 2 , (ld) d σ /d t has a smooth behaviour; neither this reaction nor the preceding one shows a clear evidence for backward events, (le) d σ /d t has a break at t = −0.5 (GeV/ c ) 2 ; there is a significant cross section in the backward region; (lf) and (lg) show mainly backward production. The polarization of the hyperon is measured in the reactions (lb), (lc), (ld) and (le) in the forward production peak. The statistics do not allow the detection of a definite structure in the polarization but the sign and magnitude are determined. An interpretation of the results is given in terms of a dual Regge model, including the effects of absorption as elaborated recently by several authors.
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Results are reported of a study of the hypercharge reactions K − p → ωΛ (la), K − p → φΛ (lb), K − p → φ ∑ o (lc), K − p → ϱ o Λ (ld), K − p → ϱ o ∑ o (le), K − p → ϱ − ∑ + (lf) in a 12 events/ub bubble chamber experiment using K − mesons of 4.25 GeV/ c momentum. Total and differential cross sections are presented as well as the density matrix elements of the peripherally produced vector meson and (except for reaction (1f)) the hyperon polarization. For reactions (1a) and (1b) an amplitude analysis is performed. The mass and the width of the ϱ−, φ− and f-meson have been determined.
FURTHER DATA FROM THIS COLLABORATION ON THESE REACTIONS WITH TEN TIMES BETTER STATISTICS ARE PRESENTED IN M. J. LOSTY ET AL., NP B133, 38 (1978).
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The K π − system produced in the reaction K p → K 0 π − p at 4.2 GeV/ c is studied using high-statistics bubble-chamber data. The spin-parity structure is analysed as a function of the K 0 π − mass up to 1.52 GeV. Production of K ∗ (890) and K ∗ (1420) is observed in helicity-0 and helicity-1 states. Contributions of natural and unnatural parity exchange are present. Considerable S-wave production is observed over the whole mass region considered. We also study the t ′ dependence of the K ∗ (890) and K ∗ (1420) amplitudes. A comparison of our results on K ∗ (890) production with the results of an analysis of charge-exchange K ∗ (890) production, allows the separation of I = 0 and I = 1 exchange amplitudes. Some qualitative remarks are made concerning K ∗ (1420) production.
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PARTIAL WAVE ANALYSIS ASSUMING SPIN-COHERENCE TO OBTAIN SPIN-PARITY STRUCTURE AND T DEPENDENCE OF P-WAVE AND D-WAVE AMPLITUDES.
Significant production of (2030) is observed in the channel K − p → (Σ K − K + from a high statistics bubble chamber exposure at 4.2 GeV/ c . The mass and width are determined to be 2024 ± 2 MeV and 16 ± 5 MeV respectively. Apart from Σ K , the only other decay channel is found to be Λ K .
ASSUMING XI(2030) HAS ISOSPIN HALF, CROSS SECTIONS CORRECTED FOR UNOBSERVED NEUTRAL DECAYS.
Heavy quarkonia are observed to be suppressed in relativistic heavy ion collisions relative to their production in p+p collisions scaled by the number of binary collisions. In order to determine if this suppression is related to color screening of these states in the produced medium, one needs to account for other nuclear modifications including those in cold nuclear matter. In this paper, we present new measurements from the PHENIX 2007 data set of J/psi yields at forward rapidity (1.2<|y|<2.2) in Au+Au collisions at sqrt(s_NN)=200 GeV. The data confirm the earlier finding that the suppression of J/psi at forward rapidity is stronger than at midrapidity, while also extending the measurement to finer bins in collision centrality and higher transverse momentum (pT). We compare the experimental data to the most recent theoretical calculations that incorporate a variety of physics mechanisms including gluon saturation, gluon shadowing, initial-state parton energy loss, cold nuclear matter breakup, color screening, and charm recombination. We find J/psi suppression beyond cold-nuclear-matter effects. However, the current level of disagreement between models and d+Au data precludes using these models to quantify the hot-nuclear-matter suppression.
J/psi invariant yield in Au+Au collisions as a function of $N_{part}$ at forward rapidity ($p_{T}$ integrated). The statistical and systematic uncertainties vary point-to-point and are listed for each measured value. An additional global systematic uncertainty is provided in each column heading, which applies to all data points per column.
J/psi nuclear modification $R_{AA}$ in Au+Au collisions as a function of $N_{part}$ at forward rapidity ($p_T$ integrated). The statistical and systematic uncertainties vary point-to-point and are listed for each measured value. An additional global systematic uncertainty is provided in each column heading, which applies to all data points per column.
J/psi invariant yield in Au+Au collisions as a function of transverse momentum for the 0-20% centrality class at forward rapidity. The statistical and systematic uncertainties vary point-to-point and are listed for each measured value. An additional global systematic uncertainty is provided in each column heading, which applies to all data points per column.
Charmonium is a valuable probe in heavy-ion collisions to study the properties of the quark gluon plasma, and is also an interesting probe in small collision systems to study cold nuclear matter effects, which are also present in large collision systems. With the recent observations of collective behavior of produced particles in small system collisions, measurements of the modification of charmonium in small systems have become increasingly relevant. We present the results of J/ψ measurements at forward and backward rapidity in various small collision systems, p+p, p+Al, p+Au and 3He+Au, at √sNN =200 GeV. The results are presented in the form of the observable RAB, the nuclear modification factor, a measure of the ratio of the J/ψ invariant yield compared to the scaled yield in p+p collisions. We examine the rapidity, transverse momentum, and collision centrality dependence of nuclear effects on J/ψ production with different projectile sizes p and 3He, and different target sizes Al and Au. The modification is found to be strongly dependent on the target size, but to be very similar for p+Au and 3He+Au. However, for 0%–20% central collisions at backward rapidity, the modification for 3He+Au is found to be smaller than that for p+Au, with a mean fit to the ratio of 0.89±0.03(stat)±0.08(syst), possibly indicating final state effects due to the larger projectile size.
J/psi nuclear modification in p+Au collisions as a function of nuclear thickness (T_A). The statistical and systematic uncertainties vary point-to-point and are listed for each measured value. An additional global systematic uncertainty is provided in each column heading, which applies to all data points per column.
Yields for J/psi production in Cu+Cu collisions at sqrt (s_NN)= 200 GeV have been measured by the PHENIX experiment over the rapidity range |y| < 2.2 at transverse momenta from 0 to beyond 5 GeV/c. The invariant yield is obtained as a function of rapidity, transverse momentum and collision centrality, and compared with results in p+p and Au+Au collisions at the same energy. The Cu+Cu data provide greatly improved precision over existing Au+Au data for J/psi production in collisions with small to intermediate numbers of participants, providing a key constraint that is needed for disentangling cold and hot nuclear matter effects.
J/psi-->e+e- invariant yield in Cu+Cu collisions as a function of p_T at mid-rapidity for the 0-20 centrality range. The statistical and systematic uncertainties vary point-to-point and are listed for each measured value. An additional global systematic uncertainty is provided in each column heading, which applies to all data points per column.
J/psi-->e+e- invariant yield in Cu+Cu collisions as a function of p_T at mid-rapidity for the 20-40 centrality range. The statistical and systematic uncertainties vary point-to-point and are listed for each measured value. An additional global systematic uncertainty is provided in each column heading, which applies to all data points per column.
J/psi-->e+e- invariant yield in Cu+Cu collisions as a function of p_T at mid-rapidity for the 40-60 centrality range. The statistical and systematic uncertainties vary point-to-point and are listed for each measured value. An additional global systematic uncertainty is provided in each column heading, which applies to all data points per column.
A search for the flavor-changing neutral-current decay $B^{+}\to K^{+}\nu\bar{\nu}$ is performed at the Belle II experiment at the SuperKEKB asymmetric energy electron-positron collider. The results are based on a data sample corresponding to an integrated luminosity of $63\,\mbox{fb}^{-1}$ collected at the $\Upsilon{(4S)}$ resonance and a sample of $9\,\mbox{fb}^{-1}$ collected at an energy $60\mathrm{\,Me\kern -0.1em V}$ below the resonance. A novel measurement method is employed, which exploits topological properties of the $B^{+}\to K^{+}\nu\bar{\nu}$ decay that differ from both generic bottom-meson decays and light-quark pair production. This inclusive tagging approach offers a higher signal efficiency compared to previous searches. No significant signal is observed. An upper limit on the branching fraction of $B^{+}\to K^{+}\nu\bar{\nu}$ of $4.1 \times 10^{-5}$ is set at the 90% confidence level.
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