Muon Pair Production Research Articles

Radiative and hadronic tetralepton production by neutrinos

We calculate characteristics of ..nu..N ..-->.. 4..mu..X and ..nu..N ..-->.. ..mu..3eX events in neutrino scattering, arising from conventional charm production accompanied by a dimuon pair from three sources: (i) radiation from the primary lepton-quark interaction, (ii) direct pair production from the subsequent hadronic interactions, deduced empirically from observed prompt muon-pair production in hadron-hadron collisions and (iii) charm-pair production from the primary lepton-quark interaction. Sources (i) and (ii) predict spectrum-averaged 4..mu.. rates of a few times 10/sup -8/ and ..mu..3e rates of order 10/sup -7/; (iii) is much smaller. These rates are smaller than the preliminary experimental estimates, but other characteristics of the two published tetralepton events are compatible with a radiative plus hadronic interpretation. We consider an additional hadronic contribution from F production with F ..-->.. phil..nu.. and phi ..-->.. ll-bar decays, that may contribute appreciably.

Scale violating effects in large qT muon pair production

We compare the hard scattering and DDT approaches to large q T and large M muon pair production, the former being valid at all q T but only to first order in α s, the latter including a sum over all orders but being valid only for q T << M. The DDT formula is rederived in the common domain of applicability of the two approaches. A numerical study indicates that the higher order effects are important for comparison with experiment.

Muon pair production in proton-nucleon interactions and new parton radiative processes

An examination of experimental data bearing on the production of muon pairs in nucleon-nucleon interactions demonstrates the existence of a large continuum for pairs with invariant masses less than 1.0 GeV/c/sup 2/. The ratio of the pairs to the production of pions, I (..mu mu..)/I (..pi../sup 0/), is of the order of 5 x 10/sup -5/ in the fragmentation region. The production of the pairs obeys Feynman scaling in the fragmentation region; the cross sections d/sup 2/sigma/dm dx are nearly the same for the interactions of 28-GeV protons and 150-GeV protons and the assumption of scaling is consistent with less detailed measurements at 400 GeV over a region of Feynman x such that 0.15 < x < 0.6 and for values of the invariant mass m < or approx. = 1.0 GeV/c/sup 2/. The invariant-mass spectrum of this continuum varies with x; the mean mass changes from about 450 MeV/c/sup 2/ at x = 0.2 to about 700 MeV/c/sup 2/ for x approx. = 0.6. The dimuon production varies with the target nucleus as A/sup 2/3/ in an x region where meson production varies as A/sup 0.55/. The production is discussed in terms of parton bremsstrahlung, the annihilation of partonmore » pairs produced by the hadron interaction (the Bjorken-Weisberg process) and line broadening of rho-meson production.« less

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.

Radiative and hadronic production of trimuons in neutrino collisions

We calculate characteristics of trimuon events in neutrino scattering, arising from conventional single-muon production accompanied by a dimuon pair from three sources: (i) radiation from the primary lepton-quark interaction, (ii) direct pair production from the subsequent hadronic interactions, deduced empirically from observed prompt muon-pair production in hadron-hadron collisions, and (iii) charm-pair production from the primary lepton-quark interaction. The first two components give a good representation of most of the ..nu..N ..-->.. ..mu../sup -/..mu../sup -/..mu../sup +/X data (the third component is small). A few trimuon events remain unexplained at muon-pair masses m (..mu../sup +/..mu../sup -/) > 1 GeV and at low hadronic energies. Same-sign dimuon and antineutrino trimuon predictions are also presented.

Lepton pair production by high-energy neutrino-hadron collisions

Using O(2, 1) techniques and the helicity formalism, the dilepton mass spectrum for muon pair and electron-muon production is calculated in standard V − A and Salam-Weinberg type weak interactions to order α 2 G 2.

The diagrammatic structure of deep inelastic scattering in asymptotically free theories

We investigate the structure of the leading diagrams in QCD. The diagrams of a simple scalar gluon model form the basis of a generalisation to the more complicated vector gluon theory. It is found that a certain set of a generalised ladder diagrams gives the standard QCD result for the non-singlet structure function in the limit x → 1. A simple brems-strahlung model is presented which forms a useful link between QCD field theory and more intuitive parton formulations. The value of a diagrammatic treatment is that it provides an accessible approach to the discussion of other processes such as the Drell-Yan mechanism for heavy muon pair production.

Comparison of trimuon production mechanisms

We compare the predictions of six models for neutrino (and antineutrino) production of trimuon events. In particular, results are given for models based on heavy-charged-lepton decays, heavy-neutral- lepton decays together with heavy-quark decays, diffractive production and decay of heavy-quark pairs, heavy-quark cascade decays, the decays of Higgs mesons, and the radiative production of muon pairs. Our comparison should help to unravel the sources of the trimuon events detected at Fermilab and CERN. We also examine the probability of explaining the so-called superevents in which the muons are extremely energetic.

Gluon effects in muon pair production

Cross section formulas for muon pair production in hadron-hadron collisions arising from quark + antiquark → off-shell photon + gluon and gluon + quark → off-shell photon + quark subprocesses are derived in the parton model. Predictions based on QCD agree rather well with the observed transverse momentum distribution of the pair.

Implications for e+e-physics and for dilepton production in pp, pp collisions if a light neutral gauge boson exists

A recently discussed class of gauge models of weak and electromagnetic interactions allows the possibility of a light neutral gauge boson, with mass in the PETRA-PEP energy range. The consequences of such a light gauge boson are investigated for the reactions e+e- to mu + mu -(e+e-). Predictions for the total cross sections and charge asymmetries are presented, covering the energy ranges of DORIS-SPEAR and PETRA-PEP. Curves are also presented for massive muon pair production cross sections in proton-proton and proton-antiproton collisions at centre-of-mass energies of 60 GeV and 200 GeV.

Production of muon pairs in the continuum region by 39.5 GeV/ cπ ±, K ±, p and [formula omitted] beams incident on a copper target

General features of the inclusive hadroproduction of muon pairs of mass greater than 1.5 GeV/ c 2 are shown. For incident π −, the data extend up to M=5.7 GeV/ c 2 (i.e. M 2/ s≈0.4). The scaling cross section M 3d σ/d M for π −N reactions is much flatter than that for pN reactions and exceeds the latter by two to three orders of magnitude at large M 2/ s.

QCD angular correlations for muon pair production

Angular distributions of muons are discussed in the framework of a QCD treatment of muon pair production in hadron-hadron collisions. The predicted angular effects are independent of the infrared behavior of QCD. Measuring them will permit one to determine whether the origin of the large transverse momentum of the pair is in the quark transverse momenta or in a constituent-constituent subprocess.

Some properties of heavy lepton families

The simplest four-quark SU(2) ⊗ U(1) models with an anomally-free heavy lepton sector can have two charged heavy leptons and one or two neutral leprons. Such models also explain the rise in R (the ratio of hadronic to muon pair production in e +e − collisions). We study some consequences of different choices of leptonic numbers for L 1 and L 2. In particular, we derive, the leptonic decay width when several final-stae leptons are massive; the cross section for e + e −→ L 1 L 2 production; the branching ratio for e + e −→ L 2 L 2→ e3μ+ missing energy .

Comparison of recent massive muon pair data with the asymptotically free parton model

We present calculations of vW 2 and of massive muon pair production cross sections in the kinematic ranges of recent experiments. These calculations test the asymptotically free parton model and excellent agreement with the data is found. Estimates of the transverse momentum 〈 q ⊥〉 μμ expected in massive dimuon experiments are made. For s = 750 GeV 2 and M μμ ≈ 10 GeV, we predict 〈 q ⊥〉 μμ ≈ 1.4 GeV/ c.

Test of Scaling in Muon-Pair Production by Hadrons

We have measured the inclusive production of massive dimuons ($7&lt;~{M}_{\ensuremath{\mu}\ensuremath{\mu}}&lt;~11$ ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^{2}$) by 200-, 300-, and 400-GeV protons incident on Cu in order to check whether the dimensionless cross section ${{M}_{\ensuremath{\mu}\ensuremath{\mu}}}^{3}{[\frac{d\ensuremath{\sigma}}{d{M}_{\ensuremath{\mu}\ensuremath{\mu}}\mathrm{dy}}]}_{y=0}$ is a function of $\frac{{{M}_{\ensuremath{\mu}\ensuremath{\mu}}}^{2}}{s}$ alone, where $s$ is the square of the c.m. energy. The results support the scaling hypothesis.

Hadronic Production of Massive Muon Pairs: Dependence on Incident-Particle Type and on Target Nucleus

Data from a study of muon pairs produced in hadron-nucleus collisions are compared with the Drell-Yan model. Comparison of dimuon production by ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ mesons on an isoscalar target shows evidence for a charge asymmetry characteristic of an isospin-nonconserving electromagnetic process. The average transverse momentum of the pairs increases smoothly with pair mass. Data taken on carbon and tin targets are used to extract the dependence on target atomic weight.

Two-photon production processes at high energy. I

We discuss the high-energy production of muon and pion pairs in e/sup +/e/sup -/ colliding beams. All important diagrams in order ..cap alpha../sup 4/ are included. The total cross section is obtained through seven-dimensional numerical integration using a convenient set of mapped covariant variables. Some distributions are given which are relevant for both current and future colliding-beam facilities.

On the Heavy Leptons as Hadron Constituents

We examine a hadron model based on the strongly interacting leptons which constitute three-quartet and have entirely integral quantum numbers. The four charged members among (p, n, A.) are identified with the heavy lepton analysed by Perl et al. with mass value -'2 GeV. The charmed partner c with mass -'3 GeV is considered as the constituent of the 1F-series. The gross feature of R-ratio, together with the jet structure and the energy crisis in e+ -e- annihilation, is nicely explained in terms of the real pair production of the charged leptons as hadron constituents, leaving the reasonable order of the hadronic background which almost vanishes above 6 Ge V. The di-muon event induced by both neutrino and anti-neutrino is considered by taking into account the characteristic interaction in the present model, which connects the leptons with the conventional leptons and is responsible for decay of leptons. The same interaction gives rise effectively to a similar process due to the neutral current, which will occur at high energies in a significant order to the usual muon production process. Finally, the possible inner relation between our leptons and the usual leptons is discussed, both of which have now vanishing baryon number. § I. Introduction In connection with recent reports on the possible existence of leptons!) and jet structures2l in e+ -e- annihilation experiment, the present author noticed in a previous note3l a hadron model based on the hypothetical leptons as hadron constituents!) As a matter of fact, a series of recent discoveries of new particles or new phenomena besides above ones, that is, the existence of a series of 1Jf particles, the characteristic rising of R-ratio or the so-called energy crisis in e+-e- annihilation and further the remarkable experimental results in lepton-hadron reactions including the existence of neutral weak current, anomalous muon pair production, the scaling violation and so on, seems now seriously to call upon the reexamination of various models for hadrons and leptons which have been proposed during the past decade. The models may be divided into two categories according as one admits the fractional quantum numbers for hadron constituents or not. The former type of models as Gell, Mann and Zweig's quark modeP) or its modified version leads us to the concept of absolute confinement of constituents in order to avoid the possible observation of the absolutely stable entities with fractional quantum numbers against the actual experimental situation. It has given rise to the current trend of seeking the theoretical possibility of the confinement. This approach is undoubtedly encouraged by the remarkable success of the simple quark model in accounting for the hadron constitution and high energy phenomena, but

Production of Massive Muon Pairs by 300- and 400-GeV Protons

We have observed muon pairs with effective masses in the range $7&lt;~{M}_{\ensuremath{\mu}\ensuremath{\mu}}&lt;~11$ GeV/${\mathit{c}}^{2}$ produced by 300- and 400-GeV protons incident on a Cu target at Fermilab. The production cross section per nucleon, $\frac{d\ensuremath{\sigma}}{d{M}_{\ensuremath{\mu}\ensuremath{\mu}}}$, for 400-GeV incident protons is found to fall from 1 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}36}$ ${\mathrm{cm}}^{2}$/(GeV/${\mathit{c}}^{2}$) at ${M}_{\ensuremath{\mu}\ensuremath{\mu}}=7.7$ GeV/${\mathit{c}}^{2}$ to 2.7 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}38}$ ${\mathrm{cm}}^{2}$/(GeV/${\mathit{c}}^{2}$) at ${M}_{\ensuremath{\mu}\ensuremath{\mu}}=11.2$ GeV/${\mathit{c}}^{2}$. We find that a significant fraction of the observed direct single muons come from high-mass dimuons.

Production of High-Mass Muon Pairs in Proton-Nucleus Collisions at 400 GeV

We report results on the production of muon pairs in the mass range 2.5 to 20 GeV in 400-GeV proton-nucleus collisions. A total of 159 events are observed in the mass range 5.5 to 11 GeV with a cross section which is in agreement with the previous observation of a high-mass dielectron continuum signal in this interval. Details on the production dynamics and comparisons with parton-model predictions are presented. Within limitations of resolution and continuum uncertainty, the dimuon mass spectrum provides no evidence for fine structure above 5 GeV.