Persistent threshold effects characterizing dimuon and hadron distributions due to charmed particle production by neutrinos

If massive charmed particles are being produced in current νN scattering experiments, their semi-leptonic decay leads to dimuon states. The production and decay of such particles in this process is examined in a parton model which has been modified to realistically incorporate the threshold due to the large mass of the charmed particle.The model then predicts threshold scaling violations which are unexpectedly large, and persist out to several hundred GeV in neutrino energy. These effects are particularly striking in the distributions of the charmed particle and its decay products, whose naive-scaling violations are so extreme as to be better described in terms of new anomalous scaling “laws”.The resultant dimuon and hadron distributions are qualitatively consistent with all trends observed in the recent dimuon experiments. Comparative tests between charm and other mechanisms for dimuon production are proposed. An important feature of these tests is their reliance on the persistent threshold effects predicted above. The present data on the muonic energy asymmetry β as a function of incoming neutrino energy is in agreement with the anomalous scaling predicted in the above model.     

On some effective mechanism for charmed particle production in neutrino and antineutrino beams

The paper describes an effective mechanism for charmed particle production in neutrino and antineutrino reactions, which consists in production of charmed virtual vector F1-meson in a weak vertex νF1μ (without suppression by the Cabibbo angle) with further strong rescattering of F1-meson on nucleon. This “quasidiffractive” mechanism should make the basic contribution to the production of charmed particles in neutrino experiments basic energies up to some hundreds of GeV. The charmed particles are mainly produced at limited momentum transfers $\text{|q}{}^2\text{| ≈ M}{}^2{}_{\mathrm{<mtext>F</mtext>}}\text{1}$ and with equal cross sections in the neutrino and antineutrino beams.     

The leading particle effect from light quark fragmentation in charm hadroproduction

The asymmetry of D^- and D⁺ meson production in π^-N scattering observed by the E791 experiment is a phenomenon typical for what is known as the leading particle effect in charm hadroproduction. We show that the phenomenon can be explained by the effect of light quark fragmentation into charmed hadrons (LQF). Meanwhile, the size of the LQF effect is estimated from the data of the E791 experiment. A comparison is made with the estimate of the LQF effect from the prompt like-sign dimuon rate in neutrino experiments. The influence of the LQF effect on the measurement of the nucleon strange distribution asymmetry from charged current charm production processes is briefly discussed. PACS 14.60.Pq; 12.15.Ff     

Predictions for semileptonic decay rates of charmed baryons in the quark confinement model

Baryons as relativistic three-quark states are investigated in the quark confinement model (QCM), a relativistic quark model based on some assumptions about hadronization and quark confinement. In the framework of the quark-diquark approximation of the three-quark structure of baryons, the main characteristics of light (noncharmed) baryons are calculated. The obtained results agree with experimental data. Predictions are also given for semileptonic decay of charmed baryons and differential production cross-sections in quasielastic neutrino scattering of charmed baryons.     

Charm production and experimental data on cosmic neutrino flux

The results of calculation of atmospheric neutrino fluxes at sea level with energies up to 10⁷ GeV are presented. The calculations were performed within the empirical model based on modern data on inclusive cross sections of pion, kaon, and charmed particle production in nucleon-air nucleus interactions, obtained in experiments on accelerators up to nucleon energies of ～20 TeV. A comparison of the calculated and experimental data on cosmic muon neutrino fluxes measured on AMANDA II shows their agreement.     

Neutrino production of charm

Cross Sections for the production of charm and bottom in neutrino (antineutrino) reactions are calculated in asymptotically free Quantum Chromodynamics. Total and differential cross sections are given for Cabibbo suppressed valence and Cabibbo favoured strange quark ocean production. The next order Quantum Chromodynamic correction to the charm production cross section is calculated. Arguments and estimates for the distribution of final state charmed hadrons are considered.     

Present status of the opera experiment for the direct observation of neutrino oscillations in the νμ → ν τ channel

The OPERA experiment (Oscillation Project with an Emulsion-Tracking Apparatus) for the direct observation of neutrino oscillations in the ν_μ → ν _τ channel has been underway at the underground laboratory in Gran Sasso since 2007. In the course of data collection, more than 3000 ν_μ interactions have been registered in emulsion detectors. Twenty charmed neutrino interaction candidates have been found. Multidimensional criteria have been developed in order to select ν _τ interactions against νμ interactions accompanied by charmed hadron production. The first results from automated PAVIKOM emulsion scanning have been obtained. We discuss the measurements of the muon charge ratio of μ⁺ to μ^?.     

On the fragmentation functions of heavy quarks into hadrons

An explicit form for the charmed quark fragmentation function D^C_c(z) into hadrons has been obtained with the help of the “reciprocity relation” and the c-quark distribution function in charmed mesons (the function calculated in terms of the Kuti-Weisskopf model). D^C_c(z) turns out to peak mainly at z close to 1. The analysis of new data on muon pair production in neutrino reactions points to such a behaviour of the D^C_c(z) function. The obtained fragmentation function, contrary to those, used earlier, leads to a charmed particle (average) multiplicity in e⁺e^?-annihilation independent of energy.     

Transverse momentum of charmed quarks produced in deep inelastic neutrino scattering

QCD predictions on the transverse momentum of charmed quarks produced in neutrino production are presented and contrasted to similar predictions of the transverse momentum of jets in electroproduction. The effects of including charmed quark mass are also considered and turn out to be significant.     

Search for charmed hadrons in neutral strange particle events in pp interactions at 19 GeV/c

A search for charmed hadrons has been made in proton-proton interactions at 19 GeV/c using events with one or two observed neutral strange particles. No evidence for charmed particles has been found. Upper limits for their production cross sections are presented.     

The invariance of CP effects under particle phase choices

Recent data give unexpectedly large cross-sections for charmed particle production at high x_F in hadron collisions. This may imply that the proton has a non-negligible uudc$\text{c}$ Fock component. The interesting consequences of such a hypothesis are explored.     

One model for magnetic solar neutrino interactions,cosmological neutrino decays,and new particle resonant production by interactions of neutrinos from Cygnus X-3

Standard model extensions which include a charged, weak-singlet scalar particle can induce an electron-neutrino magnetic moment large enough to implement the Voloshin-Vysotski-Okun solution to the solar neutrino problem and observed anticorrelation of sunspots and neutrino flux. The resonant production and decay of such a charged scalar particle by neutrinos from ultra-high energy point sources of cosmic rays such as Cygnus X-3 has been discussed in the literature as a possible source of an anomalous muon signal in deep underground detectors. We argue here that there are versions of the charged scalar model which simultaneously can accommodate the above phenomena and in addition predict a radiative neutrino decay whose lifetime is about 10²⁴ s. This value is consistent with that needed for a dark-matter neutrino of about 30 eV mass to yield a flux of UV photons which could explain several puzzling observations of H_α emission from the galactic disk and from the intergalactic HI cloud in Leo.     

Measurement of charged particle production from 450 GeV/c protons on beryllium

This paper presents the results on charged particle yields and production ratios as measured by the NA56/SPY experiment for 450 GeV/c proton interactions on beryllium targets. The data cover a secondary momentum range from 7 GeV/c to 135 GeV/c and values up to 600 MeV/c. An experimental accuracy on the measured yields in the range from 5% to 10%, depending on the beam momentum, and around 3% for the particle production ratios has been achieved. These measurements are relevant for a precise evaluation of fluxes and composition of neutrino beams at accelerators. Results on the target thickness and shape dependence are also reported. Inclusive invariant cross sections in the forward direction have been derived. Received: 12 January 1999 / Published online: 8 September 1999     

Angular correlation in charmed particle production from e+e− and subsequent decays

In view of forthcoming experiments of greater statistics and accurate particle identification we have calculated the complete angular correlation in reactions of charmed particle (pseudo-scalar, vector, axial-vector) production from e⁺e^? and their subsequenc sequential decays, including possible photonic transitions.     

Quark and particle helicities in hadronic charmed particle decays

We investigate possibilities of obtaining information on the chirality of the charm-changing current (c?s) by measuring the helicities of hadrons with spin in exclusive hadronic charmed particle decays.     

Interpretation of the new particle of the cosmic ray neutrino experiment

In order to reconcile the life time of the new particle observed in the cosmic ray neutrino experiment with its production rate, it is proposed that the particle has a new quantum number (κ) which may be assigned to leptons and hadrons. In the production of the new particle, assumed to be a heavy charged lepton,κ is conserved by creating an associated lepton-hadron pair. Suppression of theκ-violating interaction is invoked to interpret the long life time of this particle.     

Search for a 33.9 MeV/c(2) neutral particle in pion decay

The E815 (NuTeV) neutrino experiment has performed a search for a 33. 9 MeV/c(2) weakly interacting neutral particle produced in pion decay. Such a particle may be responsible for an anomaly in the timing distribution of neutrino interactions in the KARMEN experiment. E815 has searched for this particle's decays in an instrumented decay region; no evidence for this particle was found. The search is sensitive to pion branching ratios as low as 10(-13).     

Neutrino production of charmed particles in a hybrid experiment E-564

Cryogenically sensitive nuclear emulsion was placed inside the 15-foot bubble chamber of FNAL and exposed to a wide-band energy (up to 200 GeV) neutrino beam. 194 charged-current neutrino interactions and 13 decays of charmed particles were registered. Using the nuclear emulsion as a vertex detector with the good spectrometric properties of the 15-foot bubble chamber has allowed the decays of charmed particles to be effectively analysed. Attentions is focussed on the new physical results. Λ _c ⁺ baryon andD _s ⁺ meson decay channels, production of charmed ∑ _c baryons and Λ _c ⁺ via ∑ _c . For the first time an event interpreted as production of the excited (c \(\overline s\) )-state with mass ～2790 MeV/c² has been registered.