Neutral Hadrons Research Articles

Hadron production in e+e- annihilation at sqrt s =29 GeV.

Data from the High Resolution Spectrometer at the SLAC storage ring PEP have been used to study the inclusive production of baryons and mesons. Time-of-flight measurements are used to identify the charged hadrons. Neutral hadrons are identified from effective-mass peaks associated with their decay into two charged particles. Cross sections and other inclusive production characteristics are presented for π±, K±, and K0 (K¯0) mesons, and for the baryons (antibaryons) p (p¯) and Λ (Λ¯). The ratio of the inclusive cross section to the point cross section for the K0 and K¯0 mesons is R(K0,K¯0)=6.15±0.13±0.25, and for Λ and Λ¯, R(Λ,Λ¯)=0.846±0.036±0.085. The neutral-hadron differential cross sections are compared with the predictions of the Lund string model.Received 27 October 1986DOI:https://doi.org/10.1103/PhysRevD.35.2639©1987 American Physical Society

Measurement of the branching fractions of the tau lepton using a tagged sample of tau decays.

The branching fractions for the major decay modes of the lepton are measured from a sample of tagged decays selected from +- pairs produced in e+e- annihilation. The decay products of one member of the +- pair are used to identify the event. The opposite member of the pair is then included in the sample if it satisfies an invariant-mass cut and a charged-multiplicity cut. In this way, we attempt to select an unbiased sample of decays. The sample is divided into categories based on charged- and neutral-particle multiplicities, and charged-particle identification. The branching fractions are measured simultaneously, with an unfold technique and a maximum-likelihood fit, with the sum of the branching fractions constrained to be unity. The branching fractions for the decay modes - K- and - K*- are fixed at the world averages in the fit. The following branching fractions are measured: B(-e) =(19.10.81.1)%, B(-' - )=(18.30.90.8)%, B(-) =(10.01.1 *1,4)%, B(-0) =(25.81.72.5)%, B(-(n0, n>1))=(12.01.42.5)%, B(-+-) =(6.7 0.80.9)%, and B(-+- (n0,n>0)) =(6.10.80.9)%. The total branching fraction to one charged pion plus at least one neutral hadron is measured to be (37.81.21.0)%. Limits on allowed decay modes involving the meson are discussed. © 1987 The American Physical Society.

Deep penetration of a hardronic internuclear cascade into matter at high energy and design of radiation shielding for strong-current accelerators

The author explain some physical laws of the propagation of a hadronic internuclear cascade in matter at high energy at large distances from the source and we derive some approximate asymptotic expressions for the distribution function of hadronic functions. We consider the propagation of an N-component internuclear cascade (N/sub 1/ species of neutral hadrons and N-N/sub 1/ charged hadrons) in an unbounded homogeneous medium with a flat monodirectional (along the z axis) and monoenergetic (energy E/sub 0/) source of particles of species j/sub 0/, located in the plane z = O. We assume that secondary articles produced in elementary acts of interaction and decay fly out in the direction of the motion of the primary particle, which is entirely natural in the high-energy range. The system of kinetic equations that describes the cascade propagation is given.

Hadron calorimetry at the Fermilab tagged photon spectrometer facility

Hadron calorimetry apparatus and techniques as used in the Fermilab Tagged Photon Spectrometer Facility are described. This paper concentrates on the iron-acrylic scintillator device which is used in conjunction with an upstream lead-scintillator electromagnetic shower calorimeter. Distributions of energy deposit are given which can be used for Monte Carlo simulations of hadronic showers in such devices. We also present results on calibration, energy resolution and stability. The uses of the system in triggering on hadronic events in a photon beam and in the observation of neutral hadrons are described.

Can a light gluino solve the Cyg X3 puzzle?

The binary X-ray star Cyg X3, known to be source of high energy particles which produce air showers, was recently found also to originate underground muons. We propose that both air showers and underground muons are produced by the interaction in the atmosphere of a new kind of neutral, light and long-lived hadron. This hadron could be the lightest of the R-hadrons, composed by a gluino and one or more gluons, with a mass near 1 GeV. We show that this particle could easily justify the muon excess observed in the air showers above 10 15 eV associated with Cyg X3, but still have difficulties to explain the large flux of underground muons. However we believe that the idea of a hadronic nature of the primaries coming from Cyg X3 is promising and merits further experimental investigations.

Is Cygnus X-3 strange?

We discuss the recently reported measurements of the properties of high energy cosmic rays arriving from the direction of the compact binary X-ray source Cygnus X-3. We argue that the source of these events may be a strange quark star, and that the primary which directly produces them is a low baryon number neutral hadron with multiple strangeness which is stable up to (at least) simultaneous double strangeness changing weak decays.

Is there a new type of hadron with mass around 90 GeV?

Abstract It is suggested that the observed l l γ events in the Z0 mass region could actually be due to the decay and a new neutral massive hadron, ζ, with JPC = 0±-. Interestingly, the other decay modes of ζ can give rise to events with a hard photon or a monojet and missing transverse energy, similar to the ones recently observed at the p p collider.

Determination of the neutral to charged current cross-section ratio for antineutrino interactions on protons

An exposure of BEBC equipped with the hydrogen-filled TST to the v μ wide band beam at the CERN SPS has been used to study v μ interactions on free protons. About neutral induced interactions have been observed inside the hydrogen and separated into charged current, neutral current and neutral hadron interactions using a multivariate discriminant analysis based on the kinematics of the events. The neutral to charged current cross-section ratio has been determined to be R p v = 0.33 ± 0.04 . When combined with the value of R p v previously determined in the same experiment, the result is compatible with the prediction of the standard SU (2) × U (1) model for sin 2 θ W = 0.24 −0.08 +0.06 and ρ = 1.07 −0.08 +0.06. Fixing the parameter ρ = 1 yields sin 2 θ W = 0.18 ± 0.04.

Estimation of average hadron multiplicities in p-p collisions extended to very low energies

The average multiplicities of charged hadrons produced in p-p collisions have been deduced using newly parametrised inclusive cross sections. A substantial improvement has thus been achieved in the estimation of the average hadron multiplicities. In particular, at very low energies close to the production thresholds for pi +or- and kappa +, the result is consistent with the corresponding exclusive reaction data under charge and baryon-number conservation. It is also observed that there is some evidence of a real discrepancy between the bubble chamber method and the counter method for measuring multiplicities. The average multiplicities of the produced neutral hadrons are also discussed in correlation with those of charged hadrons.

Determination of the neutral to charged current cross section ratio for neutrino interactions on protons

About 2000 neutral induced interactions observed inside the hydrogen filled TST in BEBC have been analysed. The data were obtained from an exposure to the v μ wide band beam at the CERN SPS. A separation of these events into charged current, neutral current and neutral hadron induced interactions have been achieved using a multidimensional kinematic analysis. The neutral to charged current cross section ratio for v μ interactions on free protons has been determined avoiding the drastic cuts on the data inherent in previous experiments. The result R P v = 0.47 ± 0.04 is compatible with those measurements and the prediction of the standard SU (2) × U (1) model for sin 2 θ W = 0.18 ± 0.04.

Experimental upper limits on branching fractions for unexpected decay modes of theτlepton

Searches for 12 neutrinoless decay modes of the which violate lepton-number conservation have been made using the reaction e+e-+-. No evidence for lepton-number violation is observed, and we have set upper limits (90% C.L.) on the branching ratio for each decay mode. The branching-ratio limits on the radiative decays and e are 0.055 and 0.064%, respectively. For the charged lepton decays ee, eee, and, the branching ratio limits are 0.040, 0.033, 0.044, and 0.049%, respectively. Upper limits on the branching ratios for the following charged lepton + neutral hadron decays are 0 (0.037%), 0 (0.044%), eK0 (0.13%), K0 (0.10%), 0 (0.21%), and 0 (0.082%). We also use these data to search for the pair production in e+e- annihilation of some unconventional particles with masses less than about 3 GeV/c2. © 1982 The American Physical Society.

Search for direct single-photon production at large pT in photon-proton collisions at √ s = 62.4 GeV

As part of a study of large p T phenomena in photon-proton collisions at the CERN ISR, a search for direct single photon production has been performed. A statistical division of the data sample into the fraction consistent with single photon and the fraction due to multiphoton decays of neutral hadrons is accomplished by measuring the average conversion probability for the sample in a one radiation length thick converter. The fraction of the sample attributable to direct single photon production is 〈 γ/all〉 = 0.074 ± 0.012 for 6 GeV/ c < p T 10 GeV/ c, and 〈 γ/all〉 = 0.26 ± 0.04 for p T > 10 GeV/ c, with an additional systematic uncertainty of ±0.05 for both values.

Observation of planar three-jet events in e +e − annihilation and evidence for gluon bremsstrahlung

Topological distributions of charged and neutral hadrons from the reaction e + e − → multihadrons are studied at √ s of about 30 GeV. An excess of planar events is observed at a rate which cannot be explained by statistical fluctuations in the standard two-jet process. The planar events, mostly consisting of a slim jet on one side and a broader jet on the other, are shown actually to possess three-jet structure by demonstrating that the broader jet itself consists of two collinear jets in its own rest system. Detailed agreement between data and predictions is obtained if the process e +e −→q q ̄ g is taken into account. This strongly suggests gluon bremsstrahlung as the origin of the planar three-jet events. By comparison of the data with the qq̄g-model we obtain a value for the strong coupling constant of α S ( q 2 = 0.17 ± 0.04.

A determination of the neutral current coupling constants from inclusive and semi-inclusive neutrino data

Measurements of the π + π − ratio in the semi-inclusive neutral current reactions v( v) + N → v( v) + π + … have been announced from an analysis of the Gargamelle experiment. These data, when interpreted with the help of the quark-fragmentation model, allow a determination of the fundamental parameters of the neutral hadron current. Writing the interactions as L= G 2 ψ Vϵ α(1+ϵ 5)ψ V[ ψ Uϵ α u L (1+ϵ 5)+u R (1−ϵ 5) ψ u+ ψ dϵ α d L (1+ϵ 5)+d R (1−ϵ 5) ψ d ] we find u L 2 = 0.082 ± 0.035, u R 2 = 0.055 ± 0.025, d L 2 = 0.158 ± 0.035, d R 2 = 0.001 ± 0.025. These numbers are in accord with the Weinberg-Salam model for sin 2 θ ≈ 0.3 and should provide severe constraints for all models of the neutral current.

Search for New Massive Long-Lived Neutral Particles

We have carried out a search for neutral hadrons with masses approximately-greater-than2 GeV/c/sup 2/ and proper lifetimes approximately-greater-than10/sup -7/ sec in the M4 neutral beam at Fermilab. The particle masses were determined from their flight time and kinetic energy. Our upper limits for the production cross section of such particles are 10/sup -1/ to 10/sup -3/ times those for the production of psi's by protons for comparable kinematic conditions. This is the most sensitive search to date for quasistable neutral particles with masses approximately-greater-than2 GeV/c/sup 2/. (AIP)

Neutrino-proton interactions at Fermilab energies: Experimental arrangement, analysis procedures, and qualitative features of the data

The Fermilab 15-ft bubble chamber filled with hydrogen was exposed to a broad-momentum-band horn-focused neutrino beam produced by 300-GeV interacting protons. The selection procedure to choose a charged-current neutrino event sample is discussed. Less than three percent of the events are due to neutral hadron interactions. We present and experimentally test a method that can be used to identify the muon, estimate the incident neutrino energy, and eliminate most neutral-current interactions from the charged-current sample. Above 10 GeV the method produces an approximately 86% pure sample of charged-current events with an error in energy estimation of the order of 8% over a broad region of the data. In addition we establish experimentally several important properties of high-energy charged-current neutrino interactions. The hadrons are produced in a jet, the individual particles having sharply limited momenta perpendicular to the hadronic axis. The jet structure is maintained with constant properties to very high values of ${Q}^{2}$ and hadronic mass. The fraction of energy going into invisible particles is moderate, consistent with that expected. The average number of neutral pions rises linearly with the average number of charged particles.

Production of a New Hadron in 300-GeV Proton Interactions

We report the production of a new neutral hadron with a lifetime ∼ 10−13 sec in a 300-GeV proton interaction in nuclear emulsion.Received 16 April 1975DOI:https://doi.org/10.1103/PhysRevLett.34.1238©1975 American Physical Society

Weak neutral currents

Stimulated by recent indications that neutral-current effects may have been seen in high-energy neutrino reactions, we take up several issues that bear on the characterization of neutral hadron currents. Occasional guidance is sought in gauge models of the weak interactions, but the discussion is essentially phenomenological. Special emphasis is given to the question whether the neutral currents have "new" pieces, unrelated to those which appear in electromagnetism and in weak charge-changing reactions. Of particular interest here is the question: Are the neutral vector currents conserved?

The scatter focussing of multi-GeV charged particles and neutral hadrons

The multiple Coulomb scattering of charged particles and the nuclear elastic scattering of neutral hadrons may serve as a basis for the design of lenses for beams of such particles. The optical and spectral properties of such lenses are explored and numerical examples are given.

Hypercharge and isotopic-spin conservation constraints on some inclusive reactions

The conservation of hypercharge and isotopic spin is used in the approximation of a world whose only stable hadrons are the octets of baryons, antibaryons and pseudoscalar mesons to obtain upper and lower bounds on the average multiplicities of all nonisosinglet neutral stable hadrons in pp, K+p and π+p collisions. The validity of the approximation is discussed.