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DO -- antiMixing and Rare Charm Decays

Description: We review the current status of flavor-changing neutral currents in the charm sector. We focus on the standard-model predictions and identify the main sources of theoretical uncertainties in both charm mixing and rare charm decays. The potential of these observables for constraining short-distance physics in the standard model and its extensions is compromised by the presence of large nonperturbative effects. We examine the possible discovery windows in which short-distance physics can be tested and study the effects of various extensions of the standard model. The current experimental situation and future prospects are reviewed.
Date: October 6, 2003
Creator: Miller, Jeanne M & Burdman, Gustavo
Partner: UNT Libraries Government Documents Department

Universality and mX cut effects in B ->Xsl+l-

Description: The most precise comparison between theory and experiment for the B {yields} X{sub s}{ell}{sup +}{ell}{sup -} rate is in the q{sup 2} < 6 GeV{sup 2} region. The hadronic uncertainties associated with an experimentally required cut on m{sub X} potentially spoil the extraction of short distance flavor-changing neutral current couplings. We compute the m{sub X} cut dependence of d{Lambda}(B {yields} X{sub s}{ell}{sup +}{ell}{sup -})/dq{sup 2} using the B {yields} X{sub s}{gamma} shape function, and show that the effect is universal for all short distance contributions in the limit m{sub X}{sup 2} << m{sub B}{sup 2}. This universality is not spoiled by realistic values of the m{sub X} cut, nor by {alpha}{sub s} corrections. Alternatively, normalizing the B {yields} X{sub s}{ell}{sup +}{ell}{sup -} rate to B {yields} X{sub u}{ell}{bar {nu}} with the same cuts removes the main uncertainties. We find that the forward-backward asymmetry vanishes near q{sub 0}{sup 2} = 3 GeV{sup 2}.
Date: December 15, 2005
Creator: Lee, Keith S.M.; Ligeti, Zoltan; Stewart, Iain W. & Tackmann,Frank J.
Partner: UNT Libraries Government Documents Department

Flavor changing neutral currents and the third family

Description: We consider a Two Higgs Doublet Model with Flavor Changing Scalar Neutral Currents arising at the tree level. All the most important constraints are taken into account and the compatibility with the present Electroweak measurements is examined. The Flavor Changing couplings involving the third family are not constrained to be very small and this allows us to predict some interesting signals of new physics.
Date: September 16, 1996
Creator: Reina, L.
Partner: UNT Libraries Government Documents Department

D0-D bar 0 mixing and rare charm decays

Description: We review the current status of flavor-changing neutral currents in the charm sector. We focus on the standard-model predictions and identify the main sources of theoretical uncertainties in both D{sup 0} - {bar D}{sup 0} mixing and rare charm decays. The potential of these observables for constraining short-distance physics in the standard model and its extensions is compromised by the presence of large nonperturbative effects. We examine the possible discovery windows in which short-distance physics can be tested and study the effects of various extensions of the standard model. The current experimental situation and future prospects are reviewed.
Date: October 8, 2003
Creator: Burdman, Gustavo & Shipsey, Ian
Partner: UNT Libraries Government Documents Department

Observation of muonless neutrino-induced inelastic interactions

Description: The observation of inelastic interactions induced by high energy neutrinos and antineutrinos in which no muon is observed in the final state is reported. A possible, but by no means unique, interpretation of this effect is the existence of a neutral weak current. (auth)
Date: January 1, 1973
Creator: Benvenuti, A.; Cheng, D.C.; Cline, D.; Ford, W.T.; Imlay, R.; Ling, T.Y. et al.
Partner: UNT Libraries Government Documents Department

CP violation, neutral currents, and weak equivalence

Description: Within the past few months two excellent summaries sup{(1,2)} of the state of our knowledge of the weak interactions have been presented. Correspondingly, we will not attempt a comprehensive review but instead concentrate this discussion on the status of CP violation; the question of the neutral currents, and the weak equivalence principle.
Date: March 23, 1972
Creator: Fitch, V.L.
Partner: UNT Libraries Government Documents Department

Flavor Changing Neutral Currents in ttbar Decays at D\O

Description: We present a search for flavor changing neutral currents (FCNC) in decays of top quarks. The analysis is based on a search for t{bar t} {yields} {ell}'{nu}{ell}{bar {ell}} + jets ({ell},{ell}' = e, {mu}) final states using 4.1 fb{sup -1} of integrated luminosity of p{bar p} collisions at {radical} s = 1.96 TeV. We extract limits on the branching ratio B(t {yields} Zq) (q = u, c quarks), assuming anomalous tuZ or tcZ couplings. We do not observe any sign of such anomalous coupling and set a limit of B < 3.2% at 95% C.L.
Date: September 1, 2011
Creator: McGivern, C.L. & U., /Kansas
Partner: UNT Libraries Government Documents Department

A study of extraterrestrial antineutrino sources with the KamLAND detector

Description: We present the results of a search for extraterrestrial electron antineutrinos ({bar {nu}}{sub e}'s) in the energy range 8.3 MeV < E{sub {bar {nu}}}{sub e} < 30.8 MeV using the KamLAND detector. In an exposure of 4.53 kton-year, we identify 25 candidate events. All of the candidate events can be attributed to background, most importantly neutral current atmospheric neutrino interactions, setting an upper limit on the probability of {sup 8}B solar {nu}{sub e}'s converting into {bar {nu}}{sub e}'s at 5.3 x 10{sup -5} (90% C.L.). The present data also allows us to set more stringent limits on the diffuse supernova neutrino flux and on the annihilation rates for light dark matter particles.
Date: May 18, 2011
Creator: Collaboration, The KamLAND; Gando, A.; Gando, Y.; Ichimura, K.; Ikeda, H.; Inoue, K. et al.
Partner: UNT Libraries Government Documents Department

DØ hot topics

Description: The authors present recent DØ results based on approximately 1 fb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV recorded at the Fermilab Tevatron. Preliminary results on a search for the flavor changing neutral current process D{sup +} {yields} {pi}{sup +}{mu}{sup +}{mu}{sup -}, a measurement of the Cp violation parameter in B mixing, {epsilon}{sub B}, and a two sided limit on the B{sub s} oscillation frequency {Delta}m{sub s} are presented. The limits on {epsilon}{sub B} and {Beta}(D{sup +} {yields} {pi}{sup +}{mu}{sup +}{mu}{sup -}) are the world's best limits. The two sided bound on {Delta}m{sub s} is the first direct indication by a single experiment that {Delta}m{sub s} is bounded from above.
Date: May 1, 2006
Creator: Buchholz, D.
Partner: UNT Libraries Government Documents Department

Neutral current pi0 production in MiniBooNE

Description: This paper describes the analysis used to determine the neutral current {pi}{sup 0} production in MiniBooNE in bins of momentum. Additionally, a measurement of the relative coherent production of {pi}{sup 0}s is discussed. The coherent production rate is found to be (19.5 {+-}1.1 (stat) {+-}2.5 (sys))% of the total exclusive neutral current {pi}{sup 0} production rate.
Date: September 1, 2007
Creator: Link, J.M. & Tech., /Virginia
Partner: UNT Libraries Government Documents Department

Rare B Decays

Description: Recent results from Belle and BaBar on rare B decays involving flavor-changing neutral currents or purely leptonic final states are presented. Measurements of the CP asymmetries in B {yields} K*{gamma} and b {yields} s{gamma} are reported. Also reported are updated limits on B{sup +} {yields} K{sup +}{nu}{bar {nu}}, B{sup +} {yields} {tau}{sup +}{nu}, B{sup +} {yields} {mu}{sup +}{nu} and the recent measurement of B {yields} X{sub s}{ell}{sup +}{ell}{sup -}.
Date: February 24, 2006
Creator: Jackson, P.D. & U., /Victoria
Partner: UNT Libraries Government Documents Department

Searches for D0 - Anti-D0 Mixing, Rare Charm And Tau Decays

Description: I discuss the results on D{sup 0}-{bar D}{sup 0} mixing through hadronic as well as semi-leptonic charm decays, rare flavor-changing neutral currents in the charm sector and the lepton flavor violating {tau} decaying to charged lighter leptons. The results from both BABAR and Belle are presented in this review.
Date: January 25, 2007
Creator: Swain, Sanjay K.
Partner: UNT Libraries Government Documents Department

A separate SU(2) for the third family: Topflavor

Description: The authors consider the extended electroweak gauge group SU(2){sub 1}xSU(2){sub x}xU(1){sub Y} where the first and second families of fermions couple to SU(2){sub 1} while the third family couples to SU(2){sub 2}. Bounds based on precision electroweak observables and heavy gauge boson searches are placed on the new parameters of the theory. The extra gauge bosons can be as light as about a TeV and can be discovered at future colliders such as the NLC and LHC for a wide range of the parameter space. FCNC interactions are also considered.
Date: October 17, 1996
Creator: Muller, D. J. & Nandi, S.
Partner: UNT Libraries Government Documents Department

Local discrete symmetries from superstring derived models

Description: Discrete and global symmetries play an essential role in many extensions of the Standard Model, for example, to preserve the proton lifetime, to prevent flavor changing neutral currents, etc. An important question is how can such symmetries survive in a theory of quantum gravity, like superstring theory. In a specific string model the author illustrates how local discrete symmetries may arise in string models and play an important role in preventing fast proton decay and flavor changing neutral currents. The local discrete symmetry arises due to the breaking of the non-Abelian gauge symmetries by Wilson lines in the superstring models and forbids, for example dimension five operators which mediate rapid proton decay, to all orders of nonrenormalizable terms. In the context of models of unification of the gauge and gravitational interactions, it is precisely this type of local discrete symmetries that must be found in order to insure that a given model is not in conflict with experimental observations.
Date: October 1, 1996
Creator: Faraggi, A.E.
Partner: UNT Libraries Government Documents Department

Family universal anomalous U(1) in realistic superstring derived models

Description: An important issue in supersymmetry phenomenology is the suppression of squarks contributions to Flavor Changing Neutral Currents (FCNC). Recently it was noted that in some free fermionic three generation models the anomalous U(1) is family universal. It was further shown that if the D-term of the U(1){sub A} is the dominant source of supersymmetry breaking, the squark masses are indeed approximately degenerate. In this paper the author discusses the properties of the superstring models that give rise to the flavor universal anomalous U(1). The root cause for the universal U(1){sub A} is the cyclic permutation symmetry, the characteristic property of the Z{sub 2} X Z{sub 2} orbifold compactification, realized in the free fermionic models by the NAHE set of boundary condition basis vectors. The properties of the three generation models that preserve this cyclic permutation symmetry in the flavor charges are discussed. The cyclic permutation symmetry of the Z{sub 2} x Z{sub 2} orbifold compactification is proposed to be the characteristic property, of phenomenological interest, that distinguishes it from other classes of superstring compactifications.
Date: January 1, 1998
Creator: Faraggi, A.E.
Partner: UNT Libraries Government Documents Department

Signals from flavor changing scalar currents at the future colliders

Description: We present a general phenomenological analysis of a class of Two Higgs Doublet Models with Flavor Changing Neutral Currents arising at the tree level. The existing constraints mainly affect the couplings of the first two generations of quarks, leaving the possibility for non negligible Flavor Changing couplings of the top quark open. The next generation of lepton and hadron colliders will offer the right environment to study the physics of the top quark and to unravel the presence of new physics beyond the Standard Model. In this context we discuss some interesting signals from Flavor Changing Scalar Neutral Currents.
Date: November 22, 1996
Creator: Atwood, D.; Reina, L. & Soni, A.
Partner: UNT Libraries Government Documents Department

31305: Tevatron searches for compositeness

Description: Tevatron experiments have recently set or improved limits on quark and lepton compositeness. Included here are results from {radical}s = 1.8 TeV p{anti p} collider experiments D0 and CDF and from fixed target neutrino experiment CCFR, who report limits on quark-quark, quark-lepton, and quark-neutrino compositeness, respectively.
Date: November 1, 1997
Creator: Gallas, E. & Collaborations, E740 and E741
Partner: UNT Libraries Government Documents Department

Probing nucleon strangeness with parity violating electron scattering

Description: The electromagnetic and weak neutral currents display different sensitivities to various strange quark matrix elements of the nucleon. Measurements of the parity-violating electron-proton and electron-nucleus asymmetries at intermediate energies could allow one to extract limits on the nucleon's strange-quark form factors. The prospects for deriving such constraints from present and approved experiments at MIT-Bates and CEBAF, as well as the implications of such measurements for models of nucleon strangeness, are discussed.
Date: June 1, 1993
Creator: Musolf, M.
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

Single sector supersymmetry breaking

Description: We review recent work on realistic models that break supersymmetry dynamically and give rise to composite quarks and leptons, all in a single sector. These models have a completely natural suppression of flavor-changing neutral currents, and the hierarchy of Yukawa couplings is explained by the dimensionality of composite states. The generic signatures are unification of scalar masses with different quantum numbers at the compositeness scale, and lighter gaugino, Higgsino, and third-generation sfermion masses.
Date: March 18, 1999
Creator: Luty, Markus A. & Terning, John
Partner: UNT Libraries Government Documents Department

Improved single sector supersymmetry breaking

Description: Building on recent work by N. Arkani-Hamed and the present authors, we construct realistic models that break supersymmetry dynamically and give rise to composite quarks and leptons, all in a single strongly-coupled sector. The most important improvement compared to earlier models is that the second-generation composite states correspond to dimension-2 ''meson'' operators in the ultraviolet. This leads to a higher scale for flavor physics, and gives a completely natural suppression of flavor-changing neutral currents. We also construct models in which the hierarchy of Yukawa couplings is explained by the dimensionality of composite states. These models provide an interesting and viable alternative to gravity- and gauge-mediated models. The generic signatures are unification of scalar masses with different quantum numbers at the compositeness scale, and lighter gaugino, Higgsino, and third-generation squark and slepton masses. We also analyze large classes of models that give rise to both compositeness and supersymmetry breaking, based on gauge theories with confining, fixed-point, or free-magnetic dynamics.
Date: December 9, 1998
Creator: Luty, Markus A. & Terning, John
Partner: UNT Libraries Government Documents Department

Phenomenological aspects of heterotic orbifold models at one loop

Description: We provide a detailed study of the phenomenology of orbifold compactifications of the heterotic string within the context of supergravity effective theories. Our investigation focuses on those models where the soft Lagrangian is dominated by loop contributions to the various soft supersymmetry breaking parameters. Such models typically predict non-universal soft masses and are thus significantly different from minimal supergravity and other universal models. We consider the pattern of masses that are governed by these soft terms and investigate the implications of certain indirect constraints on supersymmetric models, such as flavor-changing neutral currents, the anomalous magnetic moment of the muon and the density of thermal relic neutralinos. These string-motivated models show novel behavior that interpolates between the phenomenology of unified supergravity models and models dominated by the superconformal anomaly.
Date: August 5, 2003
Creator: Birkedal-Hansen, A.; Binetruy, P.; Mambrini, Y. & Nelson, B.
Partner: UNT Libraries Government Documents Department