The polarizations of the Y(1S), Y(2S), and Y(3S) mesons are measured as a function of the charged particle multiplicity in proton-proton collisions at sqrt(s) = 7 TeV. The measurements are performed with a dimuon data sample collected in 2011 by the CMS experiment, corresponding to an integrated luminosity of 4.9 inverse femtobarns. The results are extracted from the dimuon decay angular distributions, in two ranges of Y(nS) transverse momentum (10-15 and 15-35 GeV), and in the rapidity interval abs(y) < 1.2. The results do not show significant changes from low- to high-multiplicity pp collisions, although large uncertainties preclude definite statements in the Y(2S) and Y(3S) cases.
$\Upsilon$(nS) polarization parameter $\lambda_\vartheta$ in the HX frame for $p_T$ of 10 to 15 GeV. The global uncertainties, independent of state and $N_{ch}$ bin, are also indicated.
$\Upsilon$(nS) polarization parameter $\lambda_\varphi$ in the HX frame for $p_T$ of 10 to 15 GeV. The global uncertainties, independent of state and $N_{ch}$ bin, are also indicated.
$\Upsilon$(nS) polarization parameter $\lambda_{\vartheta\varphi}$ in the HX frame for $p_T$ of 10 to 15 GeV. The global uncertainties, independent of state and $N_{ch}$ bin, are also indicated.
Final states π − Σ + , π + Σ − , π o Λ and ηΛ were studied for K − p reactions at 3.95 GeV/ c . Cross sections, angular distributions and polarizations are presented. Data for π − Σ + and π o Λ production are compared to the line-reversed πp reactions at the same beam momentum. Baryon-exchange peaks are presented for the Σ + π − , Σ − π + and Λπ o final states.
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A 7.5 GeV linearly polarized photon beam was used to study ϱ 0 production on d, n and p in the SLAC 82 inch bubble chamber. The production of ϱ 0 is found to proceed mainly via t -channel natural parity exchange and to conserve s -channel c.m.s. helicity for small t . The I = 1 contribution to the γ N → ϱ 0 t -channel amplitude is found to be small at 7.5 GeV.
ERRORS QUOTED INCLUDE BOTH STATISTICAL AND SYSTEMATIC UNCERTAINTIES.
THE FOURTH REACTION IS THE SUM OF THE FIRST THREE, NAMELY THE CLOSURE DIFFERENTIAL CROSS SECTION.
DIPION EVENTS IN THE RHO0 MASS REGION (600 TO 880 MEV).
Results onK0 and Λ production ine+e− annihilation at c.m. energies of 14, 22 and 34 GeV are presented. The shape of theK0 and Λ differential cross sections are very similar to each other and to those of π±,K± and\(p(\bar p)\). Scaling violations are observed forK0 production. We obtain a value for the probability to produce strange quark-antiquark pairs relative to that to produce up or down quark-antiquark pairs of 0.35±0.02±0.05. The value ofRh=σ(e+e-→hX)/σµµ is shown to rise steadily with c.m. energy for all particle species. At 34 GeV we find 1.48±0.05K0 and 0.31±0.03 Λ per event. We have searched for possible Λ polarization. The production ofK0's and Λ's in jets is examined as a function ofpT2 and rapidity and compared to that of all charged particles; the yields in two and three jets are also investigated. Results are presented from events with two baryons\((\Lambda ,\bar \Lambda ,por\bar p)\) observed.
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A new measurement of the differential cross section and of the analysing power A 0 n of the charge-exchange reaction p − p → n − n at 875 MeV/ c is presented. The A 0 n data cover the entire angular range and constitute a considerable improvement over previously published data, both in the forward and in the backward hemisphere. The cross-section data cover only the backward region, but are unique at this energy. A careful study of the long-term drifts of the apparatus has allowed to fully exploit the good statistics of the data.
Forward hemisphere measurement. Additional systematic error of 4 pct due to target polarization uncertainty.
Backward hemisphere measurement. Additional systematic error of 15 pct.
Differential cross section in the backward hemisphere. Additional systematic error of 15 pct.
The polarization parameter for the reaction π−p→π0n has been measured at five incident been momenta between 1.03 and GeV/c. The results are compared with predictions of recent phase-shift analyses.
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The polarization parameter in proton-proton elastic scattering has been measured at an incident momentum of 7.9 GeV/ c and four-momentum transfers in the range 0.9 < | t | < 6.5 (GeV/ c ) 2 using a high intensity unpolarized proton beam incident on a polarized proton target. The angle and momentum of the forward scattered protons were measured with a magnet spectrometer and scintillation counter hodoscopes and the angle of the recoil proton was measured using similar hodoscopes. A clean separation between the elastic scattering from free hydrogen and that coming from inelastic interactions and from interactions with complex nuclei in the target was obtained. The polarization shows substantial structure rising from zero at | t | = 1.0 (GeV/ c ) 2 to a maximum at | t | = 1.7 (GeV/ c ) 2 and then falling to zero at | t | = 2.0 (GeV/ c ) 2 . There is evidence of a further peak at | t | = 2.8 (GeV/ c ) 2 . Above | t | = 3.25 (GeV/ c ) 2 the polarization is small and consistent with zero. A comparison of these data with data obtained at other beam momenta shows that the polarization parameter has a strong momentum dependence.
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Results from a partial wave analysis of theKππ system produced in the hypercharge exchange reaction π−p→(K+π−π0)Λ at 3.95 GeV/c are presented. SignificantQ1 production is observed but no evidence is found forQ2 production thus confirming the results obtained in a previous decay Dalitz plot analysis of the same reaction. The relative phase behaviour of the 1+(Kϱ) partial waves obtained with the present analysis provides additional confirmation of the resonance interpretation of theQ1 enhancement. Information is also obtained about its production properties and the role played by the Λ polarization in the hypercharge exchange reaction. This is compared with the results obtained in the reactionK−p→(π+π−π0)Λ at 4 GeV/c.
LAMBDA POLARIZATION CALCULATED AS AVERAGE POLARIZATION OF ALL 1 + (K RHO0) PARTIAL WAVES IN THE QLOW(1240) REGION.
SPIN PARITY CONTENT OF (K PI PI) SYSTEM.
CONTRIBUTION TO THE TOTAL JP=1+ INTENSITY FROM THE K* AND RHO ISOBARS.
Lambda production is studied in K − p interactions at 32 GeV/ c . The total Λ cross section is 2.31±0.03 mb . Using the measured Λγ combinations we find that (31±4)% of all Λ's are produced via the Σ 0 → Λγ decay. About 60% of the Λ's are associated with either a N N or K K pair; about 40% of the Λ's are produced through the hypercharge annihiltion reaction K − p→ Λ + π 'a. The two-peak structure of the invariant x distribution can be related to fragmentation processes. The Λ is found to be unpolarized in the target fragmentation region, whereas a transverse polarization is observed for forward produced Λ's. As a function of p ⊥, a polarization effect is measured at medium p ⊥.
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We have investigated the final states K ∗0 (890)Σ, K ∗0 (890)Σ 0 and K ∗0 (890) Y 1 ∗0 (1385) produced in π − p interactions at 3.93 GeV/ c . We present the differential cross sections and spin density matrix elements for the resonances as functions of momentum transfer, as well as the gL and Σ 0 polarizations. The Σ 0 polarization is found to be positive and maximal. An amplitude analysis is performed for the K ∗ Λ and K ∗ Σ 0 reactions, and it is found that one natural parity transversity amplitude is dominant for the latter.
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We have searched for signatures of polarization in hadronic jets from $Z~0 \rightarrow q \bar{q}$ decays using the ``jet handedness'' method. The polar angle asymmetry induced by the high SLC electron-beam polarization was used to separate quark jets from antiquark jets, expected to be left- and right-polarized, respectively. We find no evidence for jet handedness in our global sample or in a sample of light quark jets and we set upper limits at the 95\% C.L. of 0.063 and 0.099 respectively on the magnitude of the analyzing power of the method proposed by Efremov {\it et al.}
Polarized E- beam. Events were classified as being of light or heavy flavors based on impact parameters of charged tracks measured in the vertex detector. Jet handedness are measured for helicity-based and chirality-based analysis (seetext). C=95PCT CL indicates the upper limits at the 95 PCT C.L. on the magnitudes.
The asymmetries in forward π−N, π−Δ, and K+−(Λ+Σ) photoproduction have been measured with a 16-GeV linearly polarized beam. The experimental method and the procedures for extracting cross sections and asymmetries from the data are discussed in detail. Information on the energy and momentum-transfer dependence of cross sections for natural- and unnatural-parity exchange, interference between exchanges of opposite G parity, and vector-meson dominance is obtained and discussed.
ASYMMETRIES AND DIFFERENTIAL CROSS SECTIONS FOR PION-NUCLEON PHOTOPRODUCTION WERE FIRST PUBLISHED IN D. J. SHERDEN ET AL., PRL 30, 1230 (1973) AND PRL 31, 667 (1973) (ERRATUM). THESE SLIGHTLY REVISED NUMBERS ARE INCLUDED IN THE RECORD OF THE 1973 PAPER.
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Inclusive Λ production has been studied in K − p interactions at 8.25 GeV/ c using about 69 000 events; the total cross section is found to be 3.35 ± 0.20 mb. A comparison has been made with Σ 0 and Σ(1385) inclusive production. Their influence on the inclusive Λ production is discussed. The inclusive Λ cross section and polarization is interpreted in terms of the triple-Regge model. In the target fragmentation region an effective Regge trajectory is determined which lies closer to the K than to the K ∗ . In the beam fragmentation region the cross-section data indicate an effective Regge trajectory which corresponds to the nucleon, while the polarization data require additional Regge exchanges to be present.
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We present results of a K − d experiment performed with the 81 cm Saclay deuterium bubble chamber which was exposed to a K − beam at 4 momenta between 680 and 840 MeV/ c at the CERN PS. Cross sections were measured for inelastic two- and three-body K − n reactions on the basis of 5200 events/mb. Resonance production in the three-body reactions is discussed. In addition, differential cross sections and polarisations are presented for inelastic two-body reactions.
CROSS SECTIONS FOR TWO-BODY REACTIONS.
CROSS SECTIONS FOR THREE-BODY REACTIONS.
CROSS SECTIONS FOR K- P REACTIONS.
We present results on three reactions involving neutral final states which were studied in a magnet spark chamber system. These results are: (a) differential cross section with high statistics for K − p → K 0 n at 5 GeV /c (24 000 events) and at 8 GeV/ c (11 000 events) for t′ <2.0 (GeV/ c ) 2 ; (b) differential cross section and polarization for K − p → Λπ 0 (backward peak) at 5 GeV/ c for u ′ < 1.4 GeV/ c ) 2 ; and (c) differential cross section for K − p → K 0 Δ 0 (1232) at 5 GeV /c for t′ < 1.2 ( GeV /c) 2 . We compare our results with existing data and draw some phenomenological conclusions.
Axis error includes +- 0.0/0.0 contribution (?////TP INDEPENDENT CORRECTIONS AT 5 AND 8 GEV ARE 5.143 +- 0.418 AND 4.981 +- 0.436 RESPECTIVELY).
Axis error includes +- 0.0/0.0 contribution (?////TP INDEPENDENT CORRECTIONS AT 5 AND 8 GEV ARE 5.143 +- 0.418 AND 4.981 +- 0.436 RESPECTIVELY).
Axis error includes +- 0.0/0.0 contribution (?////UP INDEPENDENT CORRECTION FACTOR IS 3.840 +- 0.323).
Differential cross sections and polarizations are presented for the reactions K − p → Λπ 0 , Λη , Λη ′ at 8.25 GeV/ c incident K − momentum. The data, which come from a high statistics experiment in the CERN 2 m bubble chamber, are compared with previous experimental results on the same reactions and with current theoretical ideas.
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We present measurements of the differential and polarization cross sections for the reactions KL0p→Ks0p, Λπ+, Σ0π+, and Λπ+π0 made in a hydrogen bubble chamber exposed to a beam of KL0 with incident momentum 550±35 MeV/c. The quasielastic data imposes additional constraints on the partial-wave analyses of the KN and K¯N systems. Our data show no strong energy-dependent effects in the region of the reported Σ(1580), JP=32− state. The phase of the forward regeneration amplitude was found to be about - 160° independent of KL0 momentum.
SYSTEMATIC ERRORS INCLUDED.
ROUGH FIT - POSSIBLY OTHER SYSTEMATIC ERRORS.
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We have measured the polarization of $\Lambda$ hyperons produced inclusively by a $\Sigma^-$ beam of 340 GeV/c momentum in nuclear targets. From a sample of 9.5 millions of identified $\Lambda$ decays, polarizations were determined in the range $x_F \gt 0.1$ and $p_t\leq 1.6$ GeV/c . The polarization w.r.t. the production normal is mainly positive for $x_F \geq 0.3$. At fixed values of $x_F$, it increases with $p_t$ to a maximum between $p_t = 0.5$ and $p_t = 1$ GeV/c , and then decreases to zero or even negative values, in sharp contrast to the plateau above $p_t = 1$ GeV/c observed in inclusive $\Lambda$ production by protons.
Measured values of the LAMBDA polarization as a function of PT in the XL range 0.1 to 0.2.
Measured values of the LAMBDA polarization as a function of PT in the XL range 0.2 to 0.3.
Measured values of the LAMBDA polarization as a function of PT in the XL range 0.3 to 0.4.
A study of the polarization of $\Lambda$ hyperons produced in inelastic pN reactions induced by the 450 GeV proton beam from the CERN SPS has been performed with t
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The$\tau$polarisation has been studied with the${\rm e^+e^-}\to \tau^+\tau^-$data collected by the DELPHI detector at LEP in
The errors are statistical and systematic combined in quadrature.
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A measurement of theτ lepton polarization and its forward-backward asymmetry at the Z0 resonance using the OPAL detector is described. The measurement is based on analyses of τ→ρντ, ττπ(K)ντ,\(\tau\to e\bar \nu _e \nu _\tau\),\(\tau\to \mu \bar \nu _\mu\nu _\tau\) andτ→a1ντ decays from a sample of 89075 e+e−→τ+τ− candidates corresponding to an integrated luminosity of 117 pb−1. Assuming that theτ lepton decays according to V-A theory, we measure the averageτ polarization at √s=MZ to be 〈P〉=(−13.0±0.9±0.9)% and theτ polarization forward-backward asymmetry to be ApolFB=(−9.4±1.0±0.4)%, where the first error is statistical and the second systematic. These results are consistent with the hypothesis of lepton universality and, when combined, can be expressed as a measurement of sin2θefflept=0.2334±0.0012 within the context of the Standard Model.
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A precision measurement of the angular distribution of the analyzing power of the reaction p + p → d + π + has been made at 0.8 GeV. It is shown that none of the existing theoretical calculations, including those which introduce resonant dibaryon amplitudes, reproduce even the qualitative features of the data. It is concluded that our data do not require dibaryon admixtures of the kind proposed for the interpretation of recent data on vector analyzing power, i T 11 (θ), of π− d elastic scattering at the same center of mass energy.
LOWER ENERGY DATA NOT IN PUBLICATION.
LOWER ENERGY DATA NOT IN PUBLICATION.
LOWER ENERGY DATA NOT IN PUBLICATION.
Asymmetries in charged-pion photoproduction from hydrogen and deuterium have been measured with 16-GeV linearly polarized photons. Considerable energy dependence is seen in the natural-parity contribution to the π−π+ ratio from deuterium, and in the unnatural-parity part of the cross section for γn→π−p. The energy dependence of this latter cross section is consistent with the expected from a conventional pion Regge trajectory.
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We have measured the asymmetry of the cross section for γp→π+n from a polarized target at 5 and 16 GeV. The range of four-momentum transfer was 0.02<~−t<~1.0 GeV2. The π+ mesons were produced in a polarized butanol target and detected with the Stanford Linear Accelerator Center 20−GeVc spectrometer. A sizable asymmetry was found at both 5 and 16 GeV, a typical value being -0.6 near −t=0.3 GeV2. A small amount of data on the asymmetry of other photoproduction processes was also obtained.
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A precision measurement of the differential cross sections $d\sigma/d\Omega$ and the linearly polarized photon asymmetry $\Sigma \equiv (d\sigma_\perp - d\sigma_\parallel) \slash (d\sigma_\perp + d\sigma_\parallel)$ for the $\vec{\gamma} p \rightarrow \pi^0p$ reaction in the near-threshold region has been performed with a tagged photon beam and almost $4\pi$ detector at the Mainz Microtron. The Glasgow-Mainz photon tagging facility along with the Crystal Ball/TAPS multi-photon detector system and a cryogenic liquid hydrogen target were used. These data allowed for a precise determination of the energy dependence of the real parts of the $S$- and all three $P$-wave amplitudes for the first time and provide the most stringent test to date of the predictions of Chiral Perturbation Theory and its energy region of agreement with experiment.
Differential cross section at W=1.0752268 GeV
Differential cross section at W=1.0773190 GeV
Differential cross section at W=1.0793464 GeV
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