Trimuon Production Research Articles

Trimuon production at the LHC

No process without a standard model (SM) background has been observed so far. As a tool in the study of a class of models containing doubly charged vector bileptons, we propose one such process that, violating lepton flavor number conservation, has no contribution from the SM: $pp\to \mu^+\mu^+\mu^- e^-$. By carefully isolating the parameters to keep them free, we are able to acquire a notion of how a possible PMNS-like matrix present in the relevant charged current parametrization could affect the observables. We find that an interesting section of the space of parameters can be explored at the current LHC in the specified conditions.

Hidden SUSY at the LHC: the light higgsino-world scenario and the role of a lepton collider

While the SUSY flavor, CP and gravitino problems seem to favor a very heavy spectrum of matter scalars, fine-tuning in the electroweak sector prefers low values of superpotential mass \mu. In the limit of low \mu, the two lightest neutralinos and light chargino are higgsino-like. The light charginos and neutralinos may have large production cross sections at LHC, but since they are nearly mass degenerate, there is only small energy release in three-body sparticle decays. Possible dilepton and trilepton signatures are difficult to observe after mild cuts due to the very soft p_T spectrum of the final state isolated leptons. Thus, the higgsino-world scenario can easily elude standard SUSY searches at the LHC. It should motivate experimental searches to focus on dimuon and trimuon production at the very lowest p_T(\mu) values possible. If the neutralino relic abundance is enhanced via non-standard cosmological dark matter production, then there exist excellent prospects for direct or indirect detection of higgsino-like WIMPs. While the higgsino-world scenario may easily hide from LHC SUSY searches, a linear e^+e^- collider or a muon collider operating in the \sqrt{s}\sim 0.5-1 TeV range would be able to easily access the chargino and neutralino pair production reactions.

Results from the CERN short baseline neutrino experiments

During the years 1994–1998, the NOMAD and CHORUS experiments were taking data in the wide band neutrino beam of the CERN-SPS. The main goal of these experiments was the search for neutrino oscillation phenomena. Results of these searches are summarised here. In addition to the oscillation search measurements of charm production have been performed. NOMAD was able to isolate a high purity charm sample by identifying the D*+ with its decay mode into the D0. A measurement of the rate of D*+ production and a study of the fragmentation process is described here CHORUS made a topological selection of charmed particles and could perform measurements of D0 and charmed baryon production in ν μ charged-current interactions and the total rate of charm production in ν ¯ μ interactions. In addition a measurement of the trimuon production rate is presented here.

Trimuon production in $\nu$ N-scattering as a probe of massive neutrinos

The lepton–number violating process ${\mbox{$ \nu_\mu $}}N{\rightarrow} \mu^- \mu^+ \mu^+ X$ is studied for the first time in connection with Majorana neutrino masses of the second generation. The sensitivity for light and heavy Majorana neutrinos is investigated. The ratio with respect to the standard model charged current process is improved by some orders of magnitude if compared to previously discussed Majorana induced $\Delta L_{\mu} = 2$ processes. Non–observation of this process in previous experiments allows to demand the effective mass to be $\langle m_{\mu \mu} \rangle \lesssim 10^{4}$ GeV, being more stringent than previously discussed direct bounds, however still unnaturally high. Therefore, in the forseeable future, indirect bounds on effective masses other than \mbox{ $\langle m_{ee} \rangle$ } will be more stringent.

Trimuon production in pp-bar collisions.

Trimuon events in pp-bar collisions are a probe of heavy flavors: certain classes of events offer clean signatures for new physics beyond bb-bar pair creation. We evaluate the expectations for trimuon production at the CERN pp-bar collider, with realistic acceptance cuts, including possible new-physics effects from t quarks, D/sup 0/-D-bar /sup 0/ mixing, fourth-generation v quarks, and bb-barcc-bar creation.

Electromagnetic production of trimuons in muon scattering: Bethe-Heitler reactions with muon and heavy-lepton pairs

We analyze the Bethe-Heitler production of muon and heavy-lepton pairs using high-energy muon beams on a variety of targets. We give results for coherent production from a nucleus, for incoherent production from individual protons and neutrons, and for deep-inelastic production. Differential distributions are presented for the final leptons and the effects of experimental cuts are considered. This work complements our previous study of trimuon production via muon radiation, Compton radiation, and hadronic final-state interactions.

Charm muoproduction with a small-angle veto

In dimuon production $\ensuremath{\mu}N\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\mu}X$ the signal from associated charm production with semileptonic charm decay is likely to be swamped by background from electromagnetic and hadronic trimuons where one muon is lost through small-angle acceptance cuts. However, if the small-angle cut is replaced by a small-angle muon veto, the calculated background drops well below the expected charm dimuon signal. For trimuon production $\ensuremath{\mu}N\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\mu}\ensuremath{\mu}X$ there is little difference between cut and veto situations; the charm signal is much smaller than background but can be separated by energy and invariant-mass cuts.

Production of lepton pairs in processes with hadronic jets

We propose a model for the production of “extra” (additional) lepton pairs in deep inelastic lepton-hadron scattering, e+e− annihilation and large pT processes. “Extra” lepton pairs are supposed to be originated by annihilations of quarks and antiquarks created during the space-time evolution of quark initiated jets. This mechanism yields predominantly dileptons with rather low masses. Predictions following from the model are compared with the recent data on trimuon production in neutrino-nucleon interactions. It is also suggested that “internal hard processes” can lead to dileptons with both small and large masses. The latter mechanism has rather small cross section but it is particularly interesting from the point of view of the simple quark-parton model.

Electromagnetic production of trimuons in deep-inelastic muon scattering. II. Hadronic-final-state interactions

We convert a hadronic neutrino-interaction trimuon model into a model for trimuon production by muon beams. This process is assumed to proceed in two independent steps: the initial electromagnetic production of a hadronic shower and its subsequent decay into ..mu../sup +/..mu../sup -/X by hadronic-final-state interactions. Event rates are calculated and we also give results for relevant distributions. The experimental determination of a rate for trimuon production in muon beams would be very useful because it would permit a cross check between neutrino and muon physics.

Trimuon production by antineutrinos

We examine the electromagnetic and hadronic contribution to antineutrino trimuon production. The μ + μ + μ − rate and distributions are in reasonable agreement with the experimental values quoted by the CDHS group for their eight events. More data is required before any detailed comparison can be made between theory and experiment.

Internal Drell-Yan mechanism for neutrino trimuon production

The authors estimate trimuon production nu N to mu - mu - mu +X by the internal Drell-Yan processes nu d to mu -u, uu to mu + mu - and nu u to mu -d, dd to mu + mu -, for d and u quarks in the same target nucleon, using a parton-model approach. This mechanism predicts energetic trimuons with little hadronic excitation at rates of order (3 mu )/( mu ) approximately 10-6.

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.

Origins of neutrino events with three muons

The experimental observation of events in neutrino scattering with three outgoing muons presents a potential challenge to S${\mathrm{U}}_{2}$\ifmmode\times\else\texttimes\fi{}${\mathrm{U}}_{1}$ gauge models, depending on the source of such events. In this paper a comprehensive study is reported of four possible modes of trimuon production (hadronic, mixed, leptonic, and trident modes). Background sources are expected to be significant and will have to be separated from other sources. Attention is also given to two trimuon events with extraordinarily energetic muons.

Results of a beam dump experiment at the CERN SPS neutrino facility

We report results from a beam dump experiment that has been performed at the CERN SPS neutrino facility using the CDHS neutrino counter detector. Limits on dimuon and trimuon production by new penetrating neutral particles are given. A new source of prompt electron and muon neutrinos has been observed giving (1.2±0.4)× 10−7 νe or νμ per incident proton with neutrino angle smaller than 1.85 mrad and Eν > 20 GeV. If these prompt neutrinos are attributed to charmed meson pair production, the inclusive DD production cross section could be of the order of 30 ωb. If axions are existing their production rate relative to π0 mesons is found to be less than 0.5 × 10−8.

Heavy-lepton cascade mechanism of trimuon production by neutrinos

Heavy-lepton cascade mechanism of trimuon production by neutrinos

Further Observation of Trimuon Production by Neutrinos and Antineutrinos

We have observed six additional trimuons in a neutrino beam and one trimuon in an antineutrino beam using the new large-angle neutrino detector (NEULAND) at Fermilab. One of the neutrino events has three very high-energy muons. The properties of the new trimuon events together with the earlier events suggest at least two qualitatively different origins for this phenomenon.

U(1) ⊗ SU(4)L⊗ SU(4)R-Based Weak-Electromagnetic Synthesis with Manifest Left-Right Symmetry

We present a gauge theory of weak and electromagnetic interactions which is based on the group U(1) \ensuremath{\bigotimes} SU${(4)}_{\mathrm{L}}$ \ensuremath{\bigotimes} SU${(4)}_{\mathrm{R}}$ and which implements manifest left-right symmetry in a natural way. The theory is characterized by a rich lepton spectrum and is consistent with recent experimental results in atomic physics and weak trimuon production. Some novel predictions of the theory are discussed.

A model for weak trimuon production

Neutrino-induced trimuon events have been interpreted by several authors as arising from cascade decay of a new lepton produced directly in neutrino reactions. We incorporate this idea in a gauge scheme based on the group Su(2) × SU(2) × U(1).

Heavy-Lepton-Cascade Interpretation of the Neutrino-Induced Trimuon Events

The experimental data on neutrino-induced trimuon production are compared with the results of a cascade model involving two heavy leptons. The agreement between theory and experiment is excellent.

Observation of a New Process with Trimuon Production by High-Energy Neutrinos

We have observed six trimuon events produced by neutrinos in the new large-angle neutrino detector (NEULAND) at Fermilab with the momenta and charges of almost all muons determined. The properties of these events strongly suggest that their origin is not hadronic but may be in the lepton sector.