\bar \Lambda Production inK − p interactions at 32 GeV/c

Antilambda production is studied inK ^? p interactions at 32 GeV/c. Both total and differential cross sections are presented. The inclusive \(\bar \Lambda \) production cross section amounts to 109±7 μb. A remarkable energy dependence is observed, σ( \(\bar \Lambda \) ) increasing by a factor of four between 14.3 and 32 GeV/c. Thep _⊥ ² distribution exhibits an exponential fall-off with a slope of 3.3±0.2 (GeV/c)^?2. Most of the \(\bar \Lambda \) 's are emitted in the forward hemisphere. The invariantx distribution increases between 14.3 and 32 GeV/c. Data are presented for \(\bar \Lambda \) production inK ^- p→Λ \(\bar \Lambda \) +X K ^- p→ \(\bar \Lambda \) K ⁿ +X, andK ^- p→ \(\bar \Lambda \) p+X.     

Comparison of strange antibaryon and strange meson production inK + p interactions at 32 GeV/c

New experimental results are presented on inclusive production properties of \(\bar \Sigma ^{ * + } \) (1385) and \(\bar \Sigma ^{ * + } \) (1385) inK ⁺ p interactions at 32 GeV/c. The analysis is based on significantly larger statistics than previously available. A comparison is also made of invariantx-distributions ofK ⁰/ \(\bar K^0 \) , \(\bar \Lambda \) and \(\bar \Xi ^ + \) and of \(\bar \Sigma ^{ * \pm } \) (1385) andK ^*+(892). These spectra exhibit regularities expected from the quark-recombination picture when it is assumed that the strange mesons and antibaryons are produced off the strange \(\bar s\) -valence-quark in the incidentK ⁺ meson. Transverse momentum distributions are also presented forK ^*+(892) and \(\bar \Sigma ^{ * \pm } \) (1385) and found to be very similar. The results on strange antibaryon average multiplicities disagree strongly with a recent version of the additive quark model.     

\bar K K and\bar p p off-shell annihilations fromK − +p → Λ + pions at 4.2 GeV/c

We have investigated the properties of off-shell \(\bar K\) K and \(\bar p\) p annihilations into pions by using the interactionsK ^? p → Λ + pions at 4.2 GeV/c. The properties considered are multiplicities, hadronic temperatures and angular distributions. These properties appear more akin to those of \(\bar p\) p annihilations in flight than to that of \(\bar p\) p annihilation at rest despite the fact that the annihilation energy is small.     

Inclusive production of neutral strange particles in\bar pp interactions at 70 GeV/c

The inclusive production ofK _s ⁰ , Λ and \(\bar \Lambda \) particles is investigated in 70 GeV/c \(\bar pp\) interactions in an experiment performed at CERN using BEBC equipped with a TST. Differential cross-sections are studied and compared with corresponding data at surrounding energies. Differences withpp data obtained at the same energy allow an estimate of theK _s ⁰ , production cross-section in annihilation processes. Evidence is also given for central \(\Lambda \bar \Lambda \) production.     

Mixings and CP violations of theB^0 - \bar B^0 system in the four-generation model

We study the mixings and CP violations in the \(B^0 - \bar B^0 \) system together with the \(K^0 - \bar K^0 \) one in the four-generation model, taking into account the ARGUS data for the \(B_d^0 - \bar B_d^0 \) mixing. We take typical six cases of the mixing hierarchy and search for the allowed regions of three phases in the 4×4KM matrix. The CP violating parameter ? _K in the \(K^0 - \bar K^0 \) system gives a severe constraint for the phases, and the smaller mixing than that in the three-generation model is predicted for the \(B_s^0 - \bar B_s^0 \) system. The asymmetry parameters for the two-body non-leptonic decays of theB ⁰ and \(\bar B^0 \) mesons are also predicted.     

Strong decays ofΨ(4.03) andΨ(4.16) as radial excitations of charmonium

Considering the signals detected at 4.03 and 4.16 GeV as radial excitations of charmonium, we study their relative decay rates intoD \(\bar D\) ,D \(\bar D^* \) ,D ^* \(\bar D\) ,D ^* \(\bar D^* \) . We point out that one can understand these two peaks as ac \(\bar c\) 3S?2D wave state system with a large mixing angle in a Coulomb+linear interquark potential. We also examine the possibility that these two signals are respectively 3S and 4S wave excitations by studying a logarithmic charmonium potential model. We show that both these interpretations lead to drastically different predictions for the Ψ (4.16) decay rates (eitherD \(\bar D^* \) +D ^* \(\bar D\) orD \(\bar D\) mode is strongly suppressed) which would be very instructive to test experimentally.     

Minijets as a further test of QCD

Perturbative QCD is shown to be in quantitative agreement with one-and two-jet production data in the range \(27 \lesssim \sqrt s \lesssim 900GeV\) GeV forP _T(jet)?5 GeV. The integrated jet yield above a fixedP _T(parton)?3 GeV accounts for the \(\bar pp\) inelastic cross section rise in the same range. QCD predictions for jet yields up to \(\sqrt s = 40TeV\) are presented and the role of non-perturbative corrections, ultimately saving unitarity, is briefly discussed.     

Neutral strange particle production in proton-proton collisions at\sqrt s = 63 GeV

The inclusive cross section for the production ofK _s ⁰ mesons, Λ and \(\bar \Lambda\) particles in proton-proton interactions at \(\sqrt s = 63\) GeV is presented. The produced particles have been detected in the full phase space. Behaviour of the longitudinal and transversal depandences of the cross sections are discussed. The total production cross sections for _s ⁰ mesons and Λ particles was determined to \(\sigma _{{\rm K}_S^0 } = (25.5 \pm 1.4)\) mb andσ _Λ =(7.8±1.2) mb respectively. A strong energy dependence of the production cross sections is observed.     

Quark-diagram estimates ofCP violation in two-body baryonicB_d^0 - \bar B_d^0 decays

CP violation in partial-decay-rate asymmetries are examined for some two-body baryonic decays of \(B_d^0 - \bar B_d^0 \) system. We discuss two feasible experimental circumstances: the symmetrice ⁺ e ^? collisions (i) on theZ ⁰ resonance to produce incoherent \(B_d^0 \bar B_d^0 \) states, and (ii) just above the ?(4S) resonance to produceC=even \(B_d^0 \bar B_d^0 \) states. Using the quark-diagram scheme, we estimate the branching ratios of those decays, and the numbers ofb \(\bar b\) pairs needed for testing theCP-violating effects for 3σ signature. We find that the promising channels may beB _d ⁰ , \(\bar B_d^0 \to p\bar p\) , \(\Delta ^ + \bar \Delta ^ - \) , \(p\bar \Delta ^ - \) , \(\Delta ^ + \bar p\) , \(n\bar n\) , \(\Delta ^0 \bar \Delta ^0 \) , \(n\bar \Delta ^0 \) , \(\Delta ^0 \bar n\) , \(\Sigma _c^ + \bar \Sigma _c^ - \) , \(\Lambda _c^ + \bar \Lambda _c^ - \) , \(\Sigma _c^ + \bar \Lambda _c^ - \) , \(\Lambda _c^ + \bar \Sigma _c^ - \) , \(\Sigma _c^0 \bar \Sigma _c^0 \) , \(\Xi _c^0 \bar \Xi _c^0 \) , which should be interesting for experimental observation.     

Gluino and squark search at Tevatron collider energies

Event rates and distributions for high mass gluinos and squarks are computed at Tevatron collider energies, imposing experimentally realisticP _T cuts. Gluino and squark masses can be probed up to 200 GeV at \(\sqrt s = 2 TeV\) , and up to about 150 GeV at \(\sqrt s = 1.6 TeV\) with the supersymmetric signal being much more enhanced relative to the standard model background than at CERN \(\bar p\) energies. If the CERN UA1 missing-p _T events are indeed indicative for the existence of gluinos and/or squarks with masses of about 50–70 GeV, then the Fermilab collider experiments should easily confirm the expected huge supersymmetric signals.     

Benchmark cross sections forp \bar p collisions at 1.8 TeV

High-energyp \(\bar p\) collisions provide many quantitative tests of the standard model. Of particular interest are “hard scattering” processes, which test not only standard model matrix elements and higher order perturbative corrections, but also the distributions of quarks and gluons in the colliding hadrons. We present detailed comparisons of data from the CERNSp \(\bar p\) S collider with theory, incorporating up-to-date parton distributions derived from recent deep inelastic scattering data. Encouraged by the excellent agreement between data and theory at \(\sqrt s \) =630GeV, we present a complete set of “benchmark” predictions for the FNALp \(\bar p\) collider at \(\sqrt s \) =1.8TeV.     

N\bar N annihilation at rest into πππ andK\bar K\pi in the3 P 0 model and selection rules on the πρ,K\bar K* and\bar KK* production

\(N\bar N\) annihilation into three pseudoscalar mesons especially πππ and \(K\bar K\pi \) are studied in the quark pair creation model or the³ P ₀ model in which two \(q\bar q\) pairs are annihilated and two \(q\bar q\) pairs are created with quantum numbers of the vacuum or³ P ₀. The correlations of two pions to form ?,f ₂ and the resonance AX(1565) which is recently found by the ASTERIX group are taken into account. A proper treatment of the symmetry among the three pions in the final state shows that the \({}^{31}S_0 p\bar p\) annihilation into ?π is suppressed in agreement with the experiment. We calculate the cosθ distribution or the distribution of the Dalitz plot as the function of the angle between the direction of emission of one decay pion in the resonance centre of mass and the line of flight of the resonance. The interferences of π⁺ρ⁺, π^?ρ⁺ and π⁰ρ⁰ in the isospin 0 channels and π^±ρ^? and π⁰ f ₂ in the isospin 1 channel reproduce the peaks. The cos θ distribution for the P-wave \(p\bar p\) annihilation into πAX depends strongly on the size of the pion since the amplitude interfers with the π^±ρ^? amplitude which is sensitive to the size of the pion. The same model qualitatively explains the \(p\bar p\) annihilation into \(K\bar K\pi \) in whichK or \(\bar K\) and π are correlated to formK* \(\bar K\) or \(\bar K\) *K final states. We can qualitatively reproduce different patterns of the cos θ distribution for theK ^*+ andK ^*0.     

Measurements of hyperon semileptonic decays at the CERN Super Proton Synchrotron

The charged hyperon beam at the CERN Super Proton Synchrotron (SPS) has been used to collect data on semileptonic decays of Σ^?, Ξ^?, andΛ. A magnetic channel selected 100 GeV/c negatively charged particles produced in the forward direction by interaction of a 210 GeV/c proton beam on a BeO target. The Σ^? and Ξ^? hyperons were concurrently identified in a DISC ?erenkov counter, and their decay products were analysed by a magnetic spectrometer. Electron-hadron discrimination was achieved by the combined use of lead glass and lead/scintillator counters, transition radiation detectors, and a ?erenkov counter. In this article we report results on the \(\Xi \to \Lambda \pi (\Lambda \to pe\bar v), \Xi \to \Lambda e\bar v(\Lambda \to p\pi ),\) and \(\Xi \to \sum ^0 e\bar v(\sum ^0 \to \Lambda \gamma ) (\Lambda \to p\pi )\) decay modes. Samples of 7,111 \(\Lambda \to pe\bar v, 2,608 \Xi \to \Lambda e\bar v\) , and \(154 \Xi \to \Sigma ^0 e\bar v\) were used in our analysis. The branching ratio measurements gave values of (8.57±0.36)×10^?4, (5.64±0.31)×10^?4, and (0.87±0.17)×10^?4 for \(\Lambda \to pe\bar v, \Xi \to \Lambda e\bar v\) , and \( \Xi \to \sum ^0 e\bar v\) , respectively. Measurements of the Λ polarization and of the centre-of-mass distributions yield the axial vector to vector form factor ratio,g ₁/f ₁=+0.70±0.03 for \(\Lambda \to pe\bar v\) , andg ₁/f ₁=+0.25±0.05 for \(\Xi \to \Lambda e\bar v\) . The effects ofq ²-dependence off ₁ andg ₁ and of radiative corrections, the measurement of the weak magnetism termf ₂, and the effect of possible second-class current terms are discussed. Results on the \(\sum \to \Lambda e\bar v\) and \(\sum \to ne\bar v\) decay modes are reported in separate articles.     

Inclusive production ofK *(892) andΣ(1385) in\bar p p interactions at 3.6 GeV/c and a test of factorization hypothesis

We present a study of the inclusive production ofK ^*(892) and ∑^t+-(1385)+cc at 3.6 GeV/c from \(\bar p\) p interactions. The sensitivity of the exposure is 35.4 events/μb. Longitudinal and transverse momentum distributions are presented. The indirect production ofK _s ⁰ from parentK ^* and that of Λ's from parent Σ(1385) are studied. The shape of thex distribution of Λ's for \(p\xrightarrow{{\bar p}}\Lambda \) are calculated from \(p\xrightarrow{p}\Lambda \) and \(p\xrightarrow{{\pi ^ - }}\Lambda \) and compared with the experimental distributions. The difference of antiparticle production cross-section ofK _s ⁰ in the central region is compared with the expectation from Mueller-Regge formalism.     

Inclusive γ and π0 production in\bar PP interactions at 32 GeV/c

The inclusive π⁰ and γ production is studied in a \(\bar PP\) experiment at 32.1 GeV/c performed in the Mirabelle bubble chamber with a sensitivity of ～2.7 events/μb. Total and topological π⁰ cross sections are presented. The π⁰ and γ longitudinal and transverse momentum distributions are obtained and compared with \(\bar PP\) data at 22.4 GeV/c andK ^± P data at 32.1 GeV/c. The inclusive π⁰ distributions are also compared to those obtained for charged pions in the same experiment.     

Crossing-odd effects in soft nucleon collisions

A complete set of the data onpp andp \(\bar p\) scattering including measurements in the Coulomb interference region are analised to discover crossingodd effects in soft collisions. It is shown that the odderon is unable to produce a significant increase in ReA/ImA at \(\sqrt s = 546\) GeV. Moreover, the data give preference to that odderon which makes negative contribution to Re \(A_{p\bar p} \) and ceases the decrease of difference inp \(\bar p\) andpp total cross-sections.     

Very high energy nucleus-nucleus collisions and multi-chain model

Inclusive and semi-inclusive production of Λ and \(\bar \Lambda\) inK ⁺ p interactions is studied at an incident momentum of 70 GeV/c. Cross sections and single particle distributions are presented and compared with data at lower energies. Scaling is observed between 32 and 70 GeV/c in the Feynmanx variable in the target and the beam fragmentation regions for Λ and \(\bar \Lambda\) inclusive production respectively. An increase of Λ ( \(\bar \Lambda\) ) production is observed in the beam (target) fragmentation regions, whereas the data at 70 and 32 GeV/c are reasonably close in the central region. The dependence of the Λ( \(\bar \Lambda\) ) polarization as a function ofx is measured and found to be in general agreement with the results at 32 GeV/c. The (Λ \(\bar \Lambda\) ) pair production cross section increases significantly from 32 to 70 GeV/c. The Λ and \(\bar \Lambda\) production associated with an identified proton is also studied.     

The constraints of non-standardWWγ couplings from FCNC processes

It was reported that the contributions of the non-standardWWγ couplings called λ_γ and \(\bar \lambda _\gamma \) to the anomalous magnetic moments and the electric dipole moments of fermions depend on regularization schemes of the loop integral. We find that this dependence does not exist in the contributions of the λ_γ and \(\bar \lambda _\gamma \) couplings to the flavor changing neutral current (FCNC) processes of quarks such asb→sγ. By utilizing the experimental upper bound of the branching ratio of the processB→K ^*γ, we obtain the allowed regions of λ_γ and \(\bar \lambda _\gamma \) that do not depend on regularization schemes of the loop integral. The cut-off independent constraints of the other non-standardWWγ couplings called Δκ_λ and \(\tilde \kappa _\gamma \) are also obtained.     

Average temperature and multiplicities ofe + e − annihilation

Hadron temperatures ofe ⁺ e ^?→h \(\bar h\) from PEP experiments at 29 GeV are estimated using theP _⊥ distribution; rather small fluctuations are found for temperatures of π,K,..., Ξ with respect to the average \(\bar T = 196 \pm 7\) MeV. A semi-empirical formula including quark content ofh is proposed to account for multiplicities of π,K, ..., Δ in terms of a unique temperature \(\bar T\) . The formula is further extended to charmed particlesD, F, J/Ψ andΛ _c without free parameters. The property \(\bar T\) ~E _cm ^1/4 holds for other experiments of DESY andCESR.