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On Quadratic Divergences in Supergravity, Vacuum Energy and theSupersymmetric Flavor Problem

Description: We examine the phenomenological consequences ofquadratically divergent contributions to the scalar potential insupergravity effective Lagrangians. We focus specifically on the effectof these corrections on the vacuum configurationof scalar fields insoftly-broken supersymmetric theory is and the role these correctionsplay in generating non-diagonal soft scalar masses. Both effects can onlybe properly studied when the divergences are regulated in a manifestlysupersymmetric manner -- something which has ths far been neglected inpast treatments. We show how a supersymmetric regularization can impactpast conclusions about both types of phenomena and discuss what types ofhigh-energy theories are likely to be safe from unwanted flavor-changingneutral current interactions in the context of supergravity theoriesderived from heterotic string compactifications.
Date: November 18, 2005
Creator: Gaillard, Mary K. & Nelson, Brent D.
Partner: UNT Libraries Government Documents Department

An Independent Measurement of the Total Active 8B Solar Neutrino Flux Using an Array of 3He Proportional Counters at the Sudbury Neutrino Observatory

Description: The Sudbury Neutrino Observatory (SNO) used an array of {sup 3}He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active ({nu}{sub x}) {sup 8}B solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54{sub -0.31}{sup +0.33}(stat){sub -0.34}{sup +0.36}(syst) x 10{sup 6} cm{sup -2}s{sup -1}, in agreement with previous measurements and standard solar models. A global analysis of solar and reactor neutrino results yields {Delta}m{sup 2} = 7.94{sub -0.26}{sup +0.42} x 10{sup -5} eV{sup 2} and {theta} = 33.8{sub -1.3}{sup +1.4} degrees. The uncertainty on the mixing angle has been reduced from SNO's previous results.
Date: June 5, 2008
Creator: Colla, SNO
Partner: UNT Libraries Government Documents Department

Results from the Sudbury Neutrino Observatory Phase III

Description: The third and last phase of the Sudbury Neutrino Observatory (SNO) used a technique independent of previous methods, to measure the rate of neutral-current interactions in heavy water and determine precisely the total active {sup 8}B solar neutrino flux. The total flux obtained is 5.54{sub -0.31}{sup +0.33}(stat){sub -0.34}{sup +0.36}(syst) x 10{sup 6} cm{sup -2}s{sup -1}, in agreement with previous measurements and standard solar models. Results from a global analysis of solar and reactor neutrino give {Delta}m{sup 2} = 7.59{sub -0.21}{sup +0.19} x 10{sup -5} eV{sup 2} and {theta} = 34.4{sub -1.2}{sup +1.3} degrees with a reduced uncertainty on the mixing angle compared to previous phases.
Date: November 3, 2008
Creator: Collaboration, SNO & Prior, G.
Partner: UNT Libraries Government Documents Department

Search for active neutrino disappearance using neutral-current interactions in the MINOS long-baseline experiment

Description: We have measured the rates and spectra of neutral-current neutrino interactions in the MINOS detectors, which are separated by 734 km. A depletion in the rate at the far site would indicate mixing between {nu}{sub {mu}} and a sterile particle. The depletion of the total neutral-current event rate at the far site is limited to be below 17% at 90% confidence level without {nu}{sub e} appearance. Assuming oscillations occur at a single mass-squared splitting, a fit to the neutral- and charged-current energy spectra shows the fraction of {nu}{sub {mu}} oscillating to a sterile neutrino is 0.28{sub -0.28}{sup +0.25}(stat.+syst.). Including {nu}{sub e} appearance at the current experimental upper bound limits the depletion to be below 21% at 90% confidence level and the fit fraction of {nu}{sub {mu}} oscillating to a sterile neutrino is 0.43{sub -0.27}{sup +0.23}(stat.+syst.).
Date: July 1, 2008
Creator: Adamson, P.; /Fermilab; Andreopoulos, C.; /Rutherford; Arms, Kregg E.; U., /Minnesota et al.
Partner: UNT Libraries Government Documents Department

Neutral current interactions in MINOS

Description: The Main Injector Neutrino Oscillation Search (MINOS) long-baseline experiment has been actively collecting beam data since 2005, having already accumulated 3 x 10{sup 20} protons-on-target (POT). The several million neutrinos per year observed at the Near detector may improve the existing body of knowledge of neutrino cross-sections and the Near-Far comparison of the observed energy spectrum neutral current events constrains oscillations into sterile neutrinos. MINOS capabilities of observing neutral current neutrino events are described and the employed methodology for event selection is discussed, along with preliminary results obtained. An outlook on the expected neutral current related contributions from MINOS is also presented.
Date: July 1, 2007
Creator: Sousa, Alexandre
Partner: UNT Libraries Government Documents Department

The Sudbury Neutrino Observatory

Description: A report is given on the status of the Sudbury Neutrino Observatory, presently under construction in the Creighton nickel mine near Sudbury, Ontario in Canada. Focus is upon the technical factors involving a measurement of the charged-current and neutral-current interactions of solar neutrinos on deuterium.
Date: September 1, 1996
Creator: Hime, A.
Partner: UNT Libraries Government Documents Department

Precision electroweak physics at future collider experiments

Description: We present an overview of the present status and prospects for progress in electroweak measurements at future collider experiments leading to precision tests of the Standard Model of Electroweak Interactions. Special attention is paid to the measurement of the {ital W} mass, the effective weak mixing angle, and the determination of the top quark mass. Their constraints on the Higgs boson mass are discussed.
Date: November 1, 1996
Creator: Baur, U. & Demarteau, M.
Partner: UNT Libraries Government Documents Department

MIGHTY MURINES: NEUTRINO PHYSICS AT VERY HIGH ENERGY MUON COLLIDERS

Description: An overview is given of the potential for neutrino physics studies through parasitic use of the intense high energy neutrino beams that would be produced at future many-TeV muon colliders. Neutrino experiments clearly cannot compete with the collider physics. Except at the very highest energy muon colliders, the main thrust of the neutrino physics program would be to improve on the measurements from preceding neutrino experiments at lower energy muon colliders, particularly in the fields of B physics, quark mixing and CP violation. Muon colliders at the 10 TeV energy scale might already produce of order 10{sup 8} B hadrons per year in a favorable and unique enough experimental environment to have some analytical capabilities beyond any of the currently operating or proposed B factories. The most important of the quark mixing measurements at these energies might well be the improved measurements of the important CKM matrix elements {vert_bar}V{sub ub}{vert_bar} and {vert_bar}V{sub cb}{vert_bar} and, possibly, the first measurements of {vert_bar}V{sub td}{vert_bar} in the process of flavor changing neutral current interactions involving a top quark loop. Muon colliders at the highest center-of-mass energies that have been conjectured, 100--1,000 TeV, would produce neutrino beams for neutrino-nucleon interaction experiments with maximum center-of-mass energies from 300--1,000 GeV. Such energies are close to, or beyond, the discovery reach of all colliders before the turn-on of the LHC. In particular, they are comparable to the 314 GeV center-of-mass energy for electron-proton scattering at the currently operating HERA collider and so HERA provides a convenient benchmark for the physics potential. It is shown that these ultimate terrestrial neutrino experiments, should they eventually come to pass, would have several orders of magnitude more luminosity than HERA. This would potentially open up the possibility for high statistics studies of any exotic particles, such as leptoquarks, that might have been ...
Date: May 5, 2000
Creator: KING,B.J.
Partner: UNT Libraries Government Documents Department

A search for sterile neutrinos in MINOS

Description: MINOS, the Main Injector Neutrino Oscillation Search, is a long baseline neutrino oscillation experiment based at Fermilab National Accelerator Laboratory. The experiment uses a neutrino beam, which is measured 1 km downstream from its origin in the Near detector at Fermilab and then 735 km later in the Far detector at the Soudan mine. By comparing these two measurements, MINOS can attain a very high precision for parameters in the atmospheric sector of neutrino oscillations. In addition to precisely determining {Delta}m{sub 23}{sup 2} and {theta}{sub 23} through the disappearance of {nu}{sub {mu}}, MINOS is able to measure {nu}{sub {mu}} {yields} {nu}{sub sterile} by looking for a deficit in the number of neutral current interactions seen in the Far detector. In this thesis, we present the results of a search for sterile neutrinos in MINOS.
Date: December 1, 2007
Creator: Osiecki, Thomas Henry & U., /Texas
Partner: UNT Libraries Government Documents Department

Search for sterile neutrino mixing in the MINOS long baseline experiment

Description: A search for depletion of the combined flux of active neutrino species over a 735 km baseline is reported using neutral-current interaction data recorded by the MINOS detectors in the NuMI neutrino beam. Such a depletion is not expected according to conventional interpretations of neutrino oscillation data involving the three known neutrino flavors. A depletion would be a signature of oscillations or decay to postulated noninteracting sterile neutrinos, scenarios not ruled out by existing data. From an exposure of 3.18 x 10{sup 20} protons on target in which neutrinos of energies between {approx}500 MeV and 120 GeV are produced predominantly as {nu}{sub {mu}}, the visible energy spectrum of candidate neutral-current reactions in the MINOS far-detector is reconstructed. Comparison of this spectrum to that inferred from a similarly selected near-detector sample shows that of the portion of the {nu}{sub {mu}} flux observed to disappear in charged-current interaction data, the fraction that could be converting to a sterile state is less than 52% at 90% confidence level (C.L.). The hypothesis that active neutrinos mix with a single sterile neutrino via oscillations is tested by fitting the data to various models. In the particular four-neutrino models considered, the mixing angles {theta}{sub 24} and {theta}{sub 34} are constrained to be less than 11{sup o} and 56{sup o} at 90% C.L., respectively. The possibility that active neutrinos may decay to sterile neutrinos is also investigated. Pure neutrino decay without oscillations is ruled out at 5.4 standard deviations. For the scenario in which active neutrinos decay into sterile states concurrently with neutrino oscillations, a lower limit is established for the neutrino decay lifetime {tau}{sub 3}/m{sub 3} > 2.1 x 10{sup -12} s/eV at 90% C.L.
Date: January 1, 2010
Creator: Adamson, P.; Andreopoulos, C.; Auty, D. J.; Ayres, D. S.; Backhouse, C.; Barnes, P. D., Jr. et al.
Partner: UNT Libraries Government Documents Department

A study of neutrino oscillations in MINOS

Description: MINOS is a long-baseline neutrino oscillations experiment located at Fermi National Accelerator Laboratory (FNAL), USA. It makes use of the NuMI neutrino beamline and two functionally identical detectors located at distances of {approx}1km and {approx}735km from the neutrino production target respectively. The Near Detector measures the composition and energy spectrum of the neutrino beam with high precision while the Far Detector looks for evidence of neutrino oscillations. This thesis presents work conducted in two distinct areas of the MINOS experiment: analysis of neutral current and charged current interactions. While charged current events are only sensitive to muon neutrino disappearance, neutral current events can be used to distinguish oscillations into sterile neutrinos from those involving only active neutrino species. A complete, preliminary neutral current study is performed on simulated data. This is followed by a more detailed investigation of neutral current neutrino interactions in the MINOS Near Detector. A procedure identifying neutral current interactions and rejecting backgrounds due to reconstruction failures is developed. Two distinct event classification methods are investigated. The selected neutral current events in the Near Detector are used to extract corrections to the neutral current cross-section in the MINOS Monte Carlo simulation as a function of energy. The resulting correction factors are consistent with unity. The main MINOS charged current neutrino disappearance analysis is described. We present the Monte Carlo tuning procedure, event selection, extrapolation from Near to Far Detector and fit for neutrino oscillations. Systematic errors on this measurement are evaluated and discussed in detail. The data are consistent with neutrino oscillations with the following parameters: 2.74 {sup +0.44}{sub -0.26} x 10{sup -3} eV{sup 2} and sin{sup 2}(2{theta}{sub 23}) > 0.87 at 68% confidence level.
Date: June 1, 2007
Creator: Raufer, Tobias Martin
Partner: UNT Libraries Government Documents Department

Search for a fourth generation charge {minus}1/3 quark via flavor changing neutral currents

Description: There is some likelihood that a light (< m{sub t}) fourth generation charge -1/3 quark (b{prime}) would decay predominantly via loop induced flavor changing neutral currents. The charged current decay of b{prime} to charm would be highly Cabibbo suppressed due to the fact that it changes the generation number by two. The D0 experiment has searched for b{prime} pair production where one or both b{prime} quarks decays via b{prime} {r_arrow} b+{gamma}, giving signatures photon + three jets and two photons + two jets. WE don not see a significant excess of such events over background. In both modes, we set an upper limit on the cross section times branching ratio that is sufficient to rule out a standard sequential b{prime} decaying predominantly via FCNC in the mass range m{sub Z}/2 < m{sub b{prime}} < m{sub Z} + m{sub b}. For b{prime} masses larger than this, the dominant FCNC decay mode is expected to be b{prime} {r_arrow} b + Z. 14 refs., 13 figs., 5 tabs.
Date: July 1, 1996
Creator: D0 Collaboration
Partner: UNT Libraries Government Documents Department

On the road to the solution of the Solar Neutrino Problem

Description: The present status of solar neutrino experiments is reviewed. The discrepancy between the experimental results and the theoretical expectations has come to be known as the Solar Neutrino Problem. Possible solutions to this problem are discussed. The next generation of solar neutrino experiments are described.
Date: August 15, 1995
Creator: Norman, E.B.
Partner: UNT Libraries Government Documents Department

Heavy quark and neutrino physics. Final technical report, FY1994--FY1998

Description: This report begins with an overview of KSU history in personnel and funding, creation of infrastructure, and physics. Then brief summaries are given for the following research projects: Fermilab E653: Measuring Charm and Beauty Decays via Hadronic Production in a Hybrid Emulsion Spectrometer; Fermilab E791: Continued Study of Heavy Flavors at TPL; Fermilab E815: Precision Measurements of Neutrino Neutral-Current Interactions Using a Sign-Selected Beam; Fermilab E872/DONUT: Direct Observation of {nu}{sub {tau}}; Fermilab E803/COSMOS: Neutrino Oscillations; KSU at the Fermilab D0 collider; Muon Collider; OJI Progress Report: Multisampling Drift Chamber.
Date: December 31, 1998
Partner: UNT Libraries Government Documents Department

Search for the fourth generation charge -1/3 quark via flavor changing neutral currents

Description: There is some likelihood that a light (< m{sub t}) fourth generation charge -1/3 quark (b{prime}) would decay predominantly via loop induced flavor changing neutral currents. The charged current decay of b{prime} to charm wuld be highly Cabibbo suppressed due to the fact that it changes the generation number by two. The D0 experiment has searched for b{prime} pair production where one or both b{prime} quarks decays via b{prime} {yields} b + {gamma}, giving signatures photon + three jets and photon + two jets. We do not see a significant excess of such events over background. In both modes, we set an upper limit on the cross section times branching ratio that is sufficient to rule out a standard sequential b{prime} decaying predominantly via FCNC in the mass range m{sub Z}/2 < m{sub b{prime}} < m{sub Z} + m{sub b}. For b{prime} masses larger than this, the dominant FCNC decay mode is expected to be b{prime} {yields} b + Z. 10 refs., 10 figs., 10 tabs.
Date: August 1, 1996
Creator: Greenlee, H.B.
Partner: UNT Libraries Government Documents Department

A small target neutrino deep-inelastic scattering experiment at the first muon collider

Description: Several different scenarios for neutrino scattering experiments using a neutrino beam from the muon collider complex are discussed. The physics reach of a neutrino experiment at the front end of a muon collider is shown to extend far beyond that of current neutrino experiments, since the high intensity neutrino beams one would see at the muon collider allow for a large flexibility in choosing neutrino targets. Measurements of quark spin, A-dependence of the structure function xF{sub 3} and neutral current chiral couplings to quarks are outlined.
Date: April 1, 1998
Creator: Harris, D.A. & McFarland, K.S.
Partner: UNT Libraries Government Documents Department

Sterile neutrino oscillations in MINOS and hadron production in pC collisions

Description: MINOS is a long baseline neutrino oscillation experiment, starting with a muon-neutrino beam, for the precise measurement of the atmospheric neutrino oscillation parameters |{Delta}m{sup 2}| and {theta}{sub 23}. The Near Detector measures the neutrino flux and spectra before oscillations. The beam propagates for 735 km to the Far Detector, which measures the depleted spectrum after oscillations. The depletion can be interpreted as {nu}{sub {mu}} {yields} {nu}{sub {tau}} oscillations. Subdominant {nu}{sub {mu}} {yields} {nu}{sub e} oscillations may be allowed if the mixing angle {theta}{sub 13} {ne} 0. The two detectors are functionally identical in order to cancel systematic errors when using the Near Detector data to constrain the Far Detector prediction. A crucial part of the analysis is the relative calibration between the two detectors, which is known at the 2% level. A calibration procedure to remove the time and temperature dependence of the detector response using through-going cosmic muons is presented here. Although the two-detector approach reduces the systematic uncertainties related to the neutrino flux, a cross check on the neutrino parent meson ratios is performed in this thesis. The cross sections of mesons produced in proton-carbon interactions from the NA49 experiment have been measured and the results have been compared to the MINOS expectations. A neutrino oscillation analysis allowing mixing to a sterile neutrino is performed, under the assumption that the additional mass splitting is {Omicron}(1 eV{sup 2}). The analysis uses the energy spectrum of the neutral current interaction products, as neutral current interactions are sensitive to sterile neutrino mixing but not to the active flavour neutrino mixing. The neutrino oscillation parameters have been found to be: |{Delta}m{sup 2}| = 2.43{sub -0.18}{sup +0.21} x 10{sup -3} eV{sup 2}, {theta}{sub 23} = 40.27{sup o}{sub -5.17}{sup +14.64}, {theta}{sub 24} = 0.00{sup o}{sup +5.99} and {theta}{sub 34} = 0.00{sup o}{sup +24.57} under ...
Date: July 1, 2010
Creator: Tinti, Gemma Maria & U., /Oxford
Partner: UNT Libraries Government Documents Department

Preliminary Proposal to Study Neutrino Interactions with Neutrons and Protons Using the 15-Foot Bubble Chamber at NAL Filled with Deuterium

Description: We propose an investigation of neutrino interactions in the deuterium filled 15-foot bubble chamber at NAL. A 250,000 picture run with 200 GeV protons should yield very interesting physics even with a 'bare' deuterium chamber. This addendum extends the physics discussion in the original proposal to the search for charm particles, and the study of neutral currents. A ({nu}{sub {mu}},d) bubble chamber exposure with E{sub P} = 200-300 GeV is the most promising experiment that can be done to search for the type of charm particles that are essential to Gauge theories of weak and electromagnetic interactions. This addendum updates and summarizes Proposal 151. We propose a 300,000 picture run of the 15-foot bubble chamber filled with deuterium exposed to a wide band, 2 horn, neutrino beam from protons of energy E{sub p} {ge} 300 GeV. The analysis will be based primarily on the bare bubble chamber data but will also use the EMI wherever useful. The physics purposes of the experiment include: (1) Extensive search for charmed baryons and mesons; Determination of the ratio of the total charged current cross sections {sigma}({nu},n)/{sigma}({nu},0); (3) Determination of d{sup 2}{sigma}{sup C.C.}/dxdy for ({nu},n) and ({nu},p) interactions separately; (4) Study of ({nu},n) and ({nu},p) neutral current interactions; and (5) Physics of Special Channels in charged current and neutral current events.
Date: July 15, 1971
Creator: Snow, G.A.; U., /Maryland; Burnstein, R.A. & /IIT
Partner: UNT Libraries Government Documents Department

A search for sterile neutrinos at the MINOS experiment

Description: MINOS is a long baseline neutrino oscillation experiment based at the Fermi National Accelerator Laboratory in Illinois, USA. The experiment was designed to study neutrino oscillation phenomena. The {nu}{sub {mu}} beam produced by the NuMI beam facility at FNAL is used along with two functionally identical detectors. The Near Detector at FNAL and a Far Detector 735 km away in the Soudan Underground Laboratory in northern Minnesota. Comparison of the observed spectra of neutrinos at the two detectors provides the evidence for neutrino oscillations. This thesis presents work on the postulated phenomena of sterile neutrinos. Oscillations between active and sterile neutrinos will lead to a deficit in the expected rate of measured Neutral Current interactions at the Far Detector. A technique for selecting Neutral Current events utilizing an Artificial Neural Network is presented with resulting overall efficiency of 91.1% and purity of 66.0%. A method of predicting the expected Charged and Neutral Current energy spectra at the Far Detector given the data recorded at the Near Detector is presented. A model to search for oscillations between sterile and active neutrinos is developed. Sources of systematic uncertainty that can effect the results of the analysis are discussed. The analysis developed is applied to a Standard Model 3 flavour oscillation model as a cross check under the scenarios with and without {nu}{sub e} appearance. The oscillation parameters measured by this model are {Delta}m{sub 32}{sup 2} = (2.39{sub -0.15}{sup +0.23}) x 10{sup -3} eV{sup 2} and {theta}{sub 23} = 0.727{sub -0.11}{sup +0.22} for the no {nu}{sub e} appearance result. An analysis of the resulting prediction reveals no evidence for active neutrino disappearance. The analysis is then performed using the 4 flavour neutrino oscillation model developed. Again this is done under the 2 scenarios of {nu}{sub e} appearance and no {nu}{sub e} appearance. The ...
Date: August 1, 2010
Creator: Pittam, Robert Neil & U., /Oxford
Partner: UNT Libraries Government Documents Department

Recent results from the MINOS experiment

Description: The MINOS experiment utilizes the NuMI beam of muon neutrinos to study the phenomenon of neutrino oscillations. Neutrinos are sent over a baseline of 735 km, with a detector near the production point at Fermilab and one at the Soudan underground laboratory in northern Minnesota. By measuring the disappearance characteristic of oscillations, MINOS has made the best measurement of the atmospheric neutrino mass splitting to date. By looking for electron neutrino appearance, a limit has been placed on the the mixing angle sin{sup 2}(2{theta}{sub 13}) of &lt; 0.29 at 90% c.l. (for {delta}{sub CP} = 0 and normal mass hierarchy). A study of neutral current interactions has allowed limits to be placed on the existence of additional, sterile neutrino flavours beyond the three of the standard oscillation model. Using the 7% muon antineutrino component of the beam, the first direct observation of muon antineutrinos in a long baseline experiment has been made, along with direct limits on the antineutrino oscillation parameters. In September 2009, the current in the NuMI focusing horns will be reversed to begin running with a dedicated antineutrino beam. This will allow the first precision measurements of the atmospheric-regime antineutrino oscillation parameters, an important test of CPT-invariance in the neutrino sector.
Date: January 1, 2009
Creator: Evans, Justin J. & London, /University Coll.
Partner: UNT Libraries Government Documents Department

A study of muon neutrino to electron neutrino oscillations in the MINOS experiment

Description: The observation of neutrino oscillations (neutrino changing from one flavor to another) has provided compelling evidence that the neutrinos have non-zero masses and that leptons mix, which is not part of the original Standard Model of particle physics. The theoretical framework that describes neutrino oscillation involves two mass scales ({Delta}m{sub atm}{sup 2} and {Delta}m{sub sol}{sup 2}), three mixing angles ({theta}{sub 12}, {theta}{sub 23}, and {theta}{sub 13}) and one CP violating phase ({delta}{sub CP}). Both mass scales and two of the mixing angles ({theta}{sub 12} and {theta}{sub 23}) have been measured by many neutrino experiments. The mixing angle {theta}{sub 13}, which is believed to be very small, remains unknown. The current best limit on {theta}13 comes from the CHOOZ experiment: {theta}{sub 13} &lt; 11{sup o} at 90% C.L. at the atmospheric mass scale. {delta}{sub CP} is also unknown today. MINOS, the Main Injector Neutrino Oscillation Search, is a long baseline neutrino experiment based at Fermi National Accelerator Laboratory. The experiment uses a muon neutrino beam, which is measured 1 km downstream from its origin in the Near Detector at Fermilab and then 735 km later in the Far Detector at the Soudan mine. By comparing these two measurements, MINOS can obtain parameters in the atmospheric sector of neutrino oscillations. MINOS has published results on the precise measurement of {Delta}m{sub atm}{sup 2} and {theta}{sub 23} through the disappearance of muon neutrinos in the Far Detector and on a search for sterile neutrinos by looking for a deficit in the number of neutral current interactions seen in the Far Detector. MINOS also has the potential to improve the limit on the neutrino mixing angle {theta}{sub 13} or make the first measurement of its value by searching for an electron neutrino appearance signal in the Far Detector. This is the focus of the study ...
Date: March 1, 2009
Creator: Yang, Tingjun
Partner: UNT Libraries Government Documents Department

Signals from flavor changing scalar neutral currents at {mu}{sup +}{mu}{sup {minus}} colliders

Description: We illustrate the possibility of observing signals from Flavor Changing Neutral Currents, originating from the scalar sector of a Two Higgs Doublet Model. In particular, we focus on the tree level process {mu}{sup +}{mu}{sup {minus}} {yields} {bar t}c + {bar c}t, via scalar exchange in the s-channel, as a distinctive process for {mu}{sup +}{mu}{sup {minus}} colliders. 12 refs., 1 fig.
Date: January 19, 1996
Creator: Reina, L.
Partner: UNT Libraries Government Documents Department

Search for b {yields} X {mu} {sup +} {mu} {sup -} and B {sup 0} {yields} {mu} {sup +} {mu} {sup -} decays in p {anti p} Collisions at {radical} s= 1.8 TeV

Description: We have searched for the flavor-changing neutral current decays b {yields} X{mu}{sup +}{mu}{sup -} and B{sup 0} {yields} {mu}{sup +}{mu}{sup -} in p{anti p} collisions at {radical}s = 1.8 TeV with the D0 detector at Fermilab. Using our observed {mu}{sup +}{mu}{sup - } mass spectrum and the measured b production cross section we determine the 90% confidence limit for the branching fraction B(b {yields} s{mu}{sup +}{mu}{sup -}) < 3.6{times}10{sup -5}. For the exclusive, purely leptonic decay B{sup 0} {yields} {mu}{sup +}{mu}{sup -} we obtain a 90% confidence level limit B(B{sup 0} {yields} {mu}{sup +}{mu}{sup -}) < 8.0{times}10{sup -6}. 9 refs., 3 figs.
Date: August 1, 1996
Creator: Abachi, S.
Partner: UNT Libraries Government Documents Department

Signals from flavor changing scalar interactions in extended models

Description: If on the one hand many predictions of the Standard Model seem to be in remarkable agreement with experiments, on the other hand the full consistency of the model needs still to be proved. In particular, given our present ignorance of the Higgs sector of the theory, extensions of the Standard Model scalar sector are worth considering. The simplest extension of adding one extra SU(2) doublet of scalar fields, i.e. the Two Higgs Doublet Model, generally introduces Flavor Changing Scalar Neutral Currents. The severe constraints imposed by the low energy physics of K and B mesons (K{sup 0} {minus} {bar K}{sup 0} and B{sup 0} {minus} {bar B}{sup 0} mixing in particular) have motivated the introduction of an unnatural discrete symmetry to avoid flavor changing scalar neutral currents. This assumption may be dropped in favor of a more natural one, which takes any flavor changing coupling to be proportional to the mass of the coupled quarks. The basic idea is that a natural hierarchy is provided by the observed fermion masses and this may be transferred to the couplings between fermions and scalar fields, even when they are not the ones directly involved in the mass generation mechanism. This report presents a Yukawa lagrangian that incorporates this assumption and describes experimental consequences, involving production of top and charm quark pairs, that would serve to test it. 9 refs., 2 figs.
Date: January 19, 1996
Creator: Reina, L.
Partner: UNT Libraries Government Documents Department