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Lepton-flavor mixing and K --> pi nu nu bar decays

Description: The impact of possible sources of lepton-flavor mixing on K {yields} {pi}{nu}{bar {nu}} decays is analyzed. At the one-loop level lepton-flavor mixing originated from non-diagonal lepton mass matrices cannot generate a CP-conserving K{sub L} {yields} {pi}{sup 0}{nu}{bar {nu}} amplitude. The rates of these modes are sensitive to leptonic flavor violation when there are at least two different leptonic mixing matrices. New interactions that violate both quark and lepton universalities could enhance the CP-conserving component of {Lambda}(K{sub L} {yields} {pi}{sup 0}{nu}{bar {nu}}) and have a substantial impact. Explicit examples of these effects in the context of supersymmetric models, with and without R-parity conservation, are discussed.
Date: November 26, 2003
Creator: Grossman, Yuval; Isidori, Gino & Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department

The future of fixed target physics: Snowmass E5 working group summary

Description: Fixed target experimentation remains a vigorous and important tool. In many cases it provides the best technique to study elementary physics. Here the authors explore several areas, where, in the near future, fixed target experiments have the potential to alter the understanding of physics. These include, but are clearly not limited to, high precision tests of CP violation in the Kaon sector, ultra-precise determination of the weak mixing angle and its evolution, and lepton flavor violation.
Date: December 10, 2002
Creator: al., Krishna Kumar et
Partner: UNT Libraries Government Documents Department

Search for neutral heavy leptons in the NuTeV experiment at Fermilab

Description: Preliminary results are presented from a search for neutral heavy leptons in the NuTeV experiment at Fermilab. The upgraded NuTeV neutrino detector for the 1996-1997 run included an instrumented decay region for the NHL search which, combined with the NuTeV calorimeter, allows detection in several decay modes ({mu}{mu}{nu}, {mu}e{nu}, {mu}{pi}, e{pi}, and ee{nu}). We see no evidence for neutral heavy leptons in our current search in the mass range from 0.3 GeV to 2.0 GeV decaying into final states containing a muon.
Date: December 1, 1998
Creator: Drucker, R.B.
Partner: UNT Libraries Government Documents Department

Study of a like-sign dilepton search for chargino-neutralino production at CDF

Description: We propose a like-sign dilepton search for chargino-neutralino production in p#22; p collisions at ps = 1:8 TeV, which complements the previously published trilepton search by the CDF detector using Fermilab Run I data. Monte Carlo predictions for the signal and background e#14;ciencies indicate a signi#12;cant increase in sensitivity to chargino-neutralino production compared to the traditional trilepton analysis alone.
Date: March 2, 1999
Creator: Worcester, Matthew
Partner: UNT Libraries Government Documents Department

Drell-Yan Lepton Pair Azimuthal Asymmetry in Hadronic Processes

Description: We study the azimuthal asymmetry in the Drell-Yan lepton pair production in hadronic scattering processes at moderate transverse momentum region, taking into account the contributions from the twist-three quark-gluon correlations from the unpolarized hadrons. The contributions are found to dominate the asymmetry, and are not power suppressed by qt/Q at small qt where qt and Q are the transverse momentum and invariant mass of the lepton pair. Accordingly, the Lam-Tung relation will be violated at this momentum region, and its violation depends on the twist-three functions. However, at large transverse momentum qt~;;Q, the Lam-Tung relation still holds because all corrections are power suppressed by Lambda2/qt2 ~;; Lambda2/Q2 where Lambda is the typical nonperturbative scale.
Date: January 22, 2009
Creator: Zhou, Jian; Yuan, Feng & Liang, Zuo-Tang
Partner: UNT Libraries Government Documents Department

Limits on tau lepton flavor violating decays in three charged leptons

Description: A search for the neutrinoless, lepton-flavor violating decay of the {tau} lepton into three charged leptons has been performed using an integrated luminosity of 468 fb{sup -1} collected with the BABAR detector at the PEP-II collider. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (1.8-3.3) x 10{sup -8} at 90% confidence level.
Date: April 29, 2010
Creator: Cervelli, Alberto
Partner: UNT Libraries Government Documents Department

Search for quark-lepton compositeness in the dimuon final state at D0

Description: We used the upgraded D0 detector at the Tevatron at {radical}s = 1.96 TeV to collect data in a search for a compositeness signature of quarks and leptons. This analysis uses an integrated luminosity of 400 pb{sup -1}. The high-mass dimuon mass spectrum is compared with that predicted by Drell-Yan (DY) scattering, modified by a contact interaction. This interaction is parameterized by a compositeness energy scale factor {Lambda}. Preliminary limits on {lambda} are set at the 95% confidence level for constructive and destructive interference between the DY amplitude and the contact interaction for various quark and lepton chiralities.
Date: January 1, 2005
Creator: Xuan, Nguyen Phuoc & U., /Notre Dame
Partner: UNT Libraries Government Documents Department

LEPTON AND PHOTON PHYSICS AT RHIC.

Description: Results on physics at RHIC using outgoing leptons and photons will be presented from Au+Au collisions at nucleon-nucleon c.m. energies {radical}(sNN) = 130 GeV and 200 GeV, and from p-p collisions at {radical}(sNN) = 200 GeV. Introduction and motivation will be presented both from the theoretical and experimental perspectives. Topics include open charm production via single e{sup {+-}}, J/{Psi} {yields} e{sup +} + e{sup -}, {mu}{sup +} + {mu}{sup -} and inclusive photon production.
Date: January 6, 2003
Creator: TANNENBAUM,M.J.
Partner: UNT Libraries Government Documents Department

Anomalous Flavor U(1)_X for Everything

Description: We present an ambitious model of flavor, based on an anomalous U(1)_X gauge symmetry with one flavon, only two right-handed neutrinos and only two mass scales: M_{grav} and m_{3/2}. In particular, there are no new scales introduced for right-handed neutrino masses. The X-charges of the matter fields are such that R-parity is conserved exactly, higher-dimensional operators are sufficiently suppressed to guarantee a proton lifetime in agreement with experiment, and the phenomenology is viable for quarks, charged leptons, as well as neutrinos. In our model one of the three light neutrinos automatically is massless. The price we have to pay for this very successful model are highly fractional X-charges which can likely be improved with less restrictive phenomenological ansatze for mass matrices.
Date: December 1, 2003
Creator: Dreiner, Herbi K.; Murayama, Hitoshi & Thormeier, Marc
Partner: UNT Libraries Government Documents Department

A Proposal to Continue Measurements of Direct Muon Production in the Forward Direction

Description: The authors recently have measured the direct muon production in the forward direction at small p{perpendicular} and find a large direct muon to pion ratio. At x = 0.3 the ratio is {mu}{sup -}/{pi}{sup -} = 1.83 {+-} 0.43 x 10{sup -4} for negatives and {mu}{sup +}/{pi}{sup +} = 6.4 {+-} 1.3 x 10{sup -5} for positives. The direct production of {mu}{sup +} and {mu}{sup -} are equal although the {pi}{sup +}/{pi}{sup -} ratios is large. They propose to continue these measurements and extend them to higher x. These new measurements would also include the A dependence of the {mu}/{pi} ratio. Based on their experience with this apparatus, they believe it is possible to extend these measurements of single lepton production to production by incident pions and kaons.
Date: October 20, 1975
Creator: Buchholz, D.; U., /Northwestern; Frisch, H.J.; Shochet, M.J.; /Chicago U., EFI; Johnson, Rolland P. et al.
Partner: UNT Libraries Government Documents Department

Photoproduction Experiment at Fermilab

Description: The authors propose to continue and extend the program of photoproduction and pair production studies currently being carried out in Experiment E-87. The goals of the physics program they propose are: (1) to look for {mu}{sup {+-}}+e{sup {-+}}{nu}'s final states; (2) to study the mass spectra of hadronic final states which are produced in association with a single charged lepton (electron or muon); and (3) to determine the properties of a selected number of photoproduced multi-body hadronic final states; in particular: {gamma} + A {yields} ({bar p}p{pi}{sup +}{pi}{sup -}) + A {yields} ({pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup 0}) + A {yields} (K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}) + A {yields} (K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup 0}) + A etec., etc. The need for a heavy lepton pair production experiment is more crucial today than when they first proposed this experiment five years ago. The {mu}e pairs observed recently at SPEAR can be interpreted as arising from the decay of 2 GeV/c{sup 2} heavy leptons. They feel there is a compelling need to demonstrate that such {mu}e pairs are observed in at least one other reaction before such an interpretation can be considered completely satisfactory. To the best of their knowledge, the only independent reaction in which one might expect to observe such events is the pair production of heavy leptons. The broad band photon beam at Fermilab is perhaps the only beam in which such a pair production experiment is feasible. In addition, the probability of mis-identifying two hadrons as a {mu}e pair is extremely small (10{sup -6}) at Fermilab energies - several orders of magnitude smaller than at SPEAR. The primary motivation for examining the photoproduced hadronic final states such as {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup 0} and K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup 0} is to search for structure in ...
Date: October 1, 1975
Creator: Knapp, B.; Lee, W.; Moscoso, L.; Sokolsky, P.; U., /Columbia; Gladding, G. et al.
Partner: UNT Libraries Government Documents Department

Lepton flavor violation

Description: The connection of rare decays to supersymmetric grand unification is highlighted, and a review of the status of rare decay experiments is given. Plans for future investigations of processes that violate lepton flavor are discussed. A new result from the MEGA experiment, a search for {mu}{sup +} {yields} e{sup +} {gamma}, is reported to be B.R. < 3.8 x 10{sup -11} with 90% confidence.
Date: October 1, 1997
Creator: Cooper, M.D. Brooks, M. & Hogan, G.E.
Partner: UNT Libraries Government Documents Department

Can lepton flavor violating interactions explain the atmospheric neutrino anomaly

Description: We investigate whether flavor changing neutrino interactions (FCNIs) can be sufficiently large to provide a viable solution to the atmospheric neutrino problem. Effective operators induced by heavy boson exchange that allow for flavor changing neutrino scattering off quarks or electrons are related by an SU(2){sub L} rotation to operators that induce anomalous tau decays. Since SU(2){sub L} violation is small for New Physics at or above the weak scale, one can use the upper bounds on lepton flavor violating tau decays or on lepton universality violation to put severe, model-independent bounds on the relevant non-standard neutrino interactions. Also Z-induced flavor changing neutral currents, due to heavy singlet neutrinos, are too small to be relevant for the atmospheric neutrino anomaly. We conclude that the FCNI solution to the atmospheric neutrino problem is ruled out.
Date: September 16, 1999
Creator: Grossman, yuval
Partner: UNT Libraries Government Documents Department

U(2) flavor physics without U(2) symmetry

Description: The authors present a model of fermion masses based on a minimal, non-Abelian discrete symmetry that reproduces the Yukawa matrices usually associated with U(2) theories of flavor. Mass and mixing angle relations that follow from the simple form of the quark and charged lepton Yukawa textures are therefore common to both theories. They show that the differing representation structure of the horizontal symmetry allows for new solutions to the solar and atmospheric neutrino problems that do not involve modification of the original charged fermion Yukawa textures, or the introduction of sterile neutrinos.
Date: October 1, 1999
Creator: Aranda, A.; Carone, C.D. & Lebed, R.F.
Partner: UNT Libraries Government Documents Department

Time Dependent B{sub s}{sup 0}-{bar B}{sub s}{sup 0} Mixing Using Inclusive and Semileptonic B Decays at SLD

Description: We set a preliminary 95% C.L. exclusion on the oscillation frequency of B{sub s}{sup 0}-{bar B}{sub s}{sup 0} mixing using a sample of 350,000 hadronic Z{sup 0} decays collected by the SLD experiment at the SLC during the 1997-98 run. The analyses determine the b-hadron flavor at production by exploiting the large forward-backward asymmetry of polarized Z{sup 0} {yields} b{bar b} decays as well as information from the hemisphere opposite that of the reconstructed B decay. In one analysis, B decay vertices are reconstructed inclusively with a new topological technique, and separation between B{sub s}{sup 0} and {bar B}{sub s}{sup 0} decays exploits the B{sub s}{sup 0} {yields} D{sub s}{sup -} cascade charge structure. In the other analysis, semileptonic decays are selected and the B decay point is reconstructed by intersecting a lepton track with the trajectory of a topologically reconstructed D meson. The two analyses are combined with a third analysis described elsewhere to exclude the following values of the B{sub s}{sup 0}-{bar B}{sub s}{sup 0} mixing oscillation frequency: {Delta}m{sub s} &lt; 5.2 ps{sup -1} and 11.3 &lt; {Delta}m{sub s} &lt; 14.2 ps{sup -1} at the 95% confidence level.
Date: September 14, 1999
Creator: Willocq, Stephane
Partner: UNT Libraries Government Documents Department

tau-mu Flavor Violation as a Probe of the Scale of New Physics

Description: Motivated by recent experimental indications of large {nu}{sub {mu}} - {nu}{tau} mixing, we explore current bounds on the analogous mixing in the charged lepton sector. We present a general formalism for dimension-6 fermionic effective operators involving {tau}-{mu} mixing with typical Lorentz structures and discuss their relationship to the standard model gauge symmetry. We find the low-energy constraints on the new physics scale associated with each operator, mostly from current experimental bounds on rare decay processes of {tau}, hadrons or heavy quarks. For operators involving at least one light quark (u, d, s), these constraints typically give a bound on the new physics scale of a few TeV or higher. Those operators with two heavy quarks turn out to be more weakly constrained at present, giving bounds of a few hundred GeV. A few scalar and pseudo-scalar operators are not subject to any current experimental constraints.
Date: April 1, 2002
Creator: Black, Deirdre; Han, Tao; He, Hong-Jian & Sher, Marc
Partner: UNT Libraries Government Documents Department

Transverse spin dependent Drell-Yan in QCD to O({alpha}{sub s}{sup 2}) at arge p{sub T} (I). Virtual corrections and methods for the real emissions

Description: The authors investigate the role of the transverse spin dependence in Drell Yan lepton pair production to NLO in QCD at parton level. In their analysis the authors deal with the large p{sub T} distributions. They give very compact expressions for the virtual O({alpha}{sub s}{sup 2}) corrections to the cross section and show that the singularities factorize. The study is performed in the {ovr MS} scheme in Dimensional Regularization, and with the t'Hooft-Veltman prescription for {gamma}{sub 5}. A discussion of the structure of the real emissions is included, and detailed methods for the study of these contributions are formulated.
Date: September 1, 1997
Creator: Chang, Sanghyeon; Coriano, Claudio & Elwood, John K.
Partner: UNT Libraries Government Documents Department

Vector Boson Pair Production in Hadronic Collisions at Order alpha(s): Lepton Correlations and Anomalous Couplings

Description: We present cross sections for production of electroweak vector boson pairs, WW, WZ and ZZ, in p{bar p} and pp collisions, at next-to-leading order in {alpha}{sub s}. We treat the leptonic decays of the bosons in the narrow-width approximation, but retain all spin information via decay angle correlations. We also include the effects of WWZ and WW{gamma} anomalous couplings.
Date: July 13, 1999
Creator: Dixon, Lance
Partner: UNT Libraries Government Documents Department