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Search for rare leptonic B decays at the Tevatron

Description: Results of a search for the Flavor-Changing Neutral Current decay B{sub s,d}{sup 0} {yields} {mu}{sup +}{mu}{sup -} using p{bar p} collision data at {radical}s = 1.96 TeV collected at Fermilab Tevatron collider by the CDF and D0 detectors are presented. CDF reports upper limits on {Beta}(B{sub s}{sup 0} {yields} {mu}{sup +}{mu}{sup -}) {le} 7.5 {center_dot} 10{sup -7} and {Beta}(B{sub d}{sup 0} {yields} {mu}{sup +}{mu}{sup -}) {le} 1.9 {center_dot} 10{sup -7} at the 95% C.L. using 171 pb{sup -1}. The D0 Collaboration used 240 pb{sup -1} to set an even more stringent limit on the branching ratio for B{sub s}{sup 0} {yields} {mu}{sup +}{mu}{sup -} of 5.0 {center_dot} 10{sup -7} at the 95% C.L..
Date: November 1, 2004
Creator: Bernhard, Ralf Patrick & U., /Zurich
Partner: UNT Libraries Government Documents Department

Radiation damage studies for the D0 silicon detector

Description: We report on irradiation studies performed on spare production silicon detector modules for the current D0 silicon detector. The lifetime expectations due to radiation damage effects of the existing silicon detector are reviewed. A new upgrade project was started with the goal of a complete replacement of the existing silicon detector. In that context, several investigations on the radiation hardness of new prototype silicon microstrip detectors were carried out. The irradiation on different detector types was performed with 10 MeV protons up to fluences of 10{sup 14} p/cm{sup 2} at the J.R. Mcdonald Laboratory at Kansas State University. The flux calibration was carefully checked using different normalization techniques. As a result, we observe roughly 40-50% less radiation damage in silicon for 10 MeV p exposure than it is expected by the predicted NIEL scaling.
Date: January 1, 2004
Creator: Lehner, F. & U., /Zurich
Partner: UNT Libraries Government Documents Department

Two-Loop Fermionic Corrections to Heavy-Quark Pair Production: theQuark-Antiquark Channel

Description: We evaluate the fermionic two-loop QCD corrections to the heavy-quark pair production process in the quark-antiquark channel. We obtain analytic results which are valid for any value of the Mandelstam invariants s and t, and of the heavy quark mass m. Our findings confirm previous results for the analytic evaluation in the small-mass limit and numerical results for the exact amplitude. We furthermore provide the expansion of the two-loop amplitude at the production threshold s {approx}> 4m{sup 2}.
Date: August 1, 2008
Creator: Bonciani, R.; Ferroglia, A.; Gehrmann, T.; U., /Zurich; Maitre, D.; /SLAC et al.
Partner: UNT Libraries Government Documents Department

Collider searches and cosmology in the MSSM with heavy scalars

Description: In a variety of supersymmetric extensions of the Standard Model, the scalar partners of the quarks and leptons are predicted to be very heavy and beyond the reach of next-generation colliders. For instance, the realization of electroweak baryogenesis in supersymmetry requires new sources of CP-violation, which can only be naturally accommodated with electric dipole moment constraints if the first and second generation scalar fermions are beyond the TeV scale. Also in focus-point supersymmetry and split supersymmetry the scalar fermions are very heavy. In this work, the phenomenology of scenarios with electroweak baryogenesis and in the focus point region at the LHC and ILC is studied, which becomes challenging due to the presence of heavy scalar fermions. Implications for the analysis of baryogenesis and dark matter are deduced. It is found that precision measurements of superpartner properties allow an accurate determination of the dark matter relic density in both scenarios, while important but only incomplete information about the baryogenesis mechanism can be obtained.
Date: August 1, 2006
Creator: Carena, Marcela; /Fermilab; Freitas, A. & U., /Zurich
Partner: UNT Libraries Government Documents Department

The SUSY-QCD coupling relation

Description: In order to establish supersymmetry at future colliders, it is not sufficient to discover new particles, but the identity of gauge couplings and the corresponding Yukawa couplings between gauginos, sfermions and fermions needs to be verified. In detailed studies it was found that the SUSY-Yukawa couplings of the electroweak sector can be studied with great precision at the ILC, but a similar analysis for the Yukawa coupling of the SUSY-QCD sector proves to be far more challenging. Here a first phenomenological study for determining this coupling is presented, using a method which combines information from LHC and ILC.
Date: October 1, 2006
Creator: Freitas, A.; U., /Zurich; Skands, P.Z. & /Fermilab
Partner: UNT Libraries Government Documents Department

Testing the SUSY-QCD Yukawa coupling in a combined LHC/ILC analysis

Description: In order to establish supersymmetry (SUSY) at future colliders, the identity of gauge couplings and the corresponding Yukawa couplings between gauginos, sfermions and fermions needs to be verified. Here a first phenomenological study for determining the Yukawa coupling of the SUSY-QCD sector is presented, using a method which combines information from LHC and ILC.
Date: September 1, 2006
Creator: Freitas, A.; U., /Zurich; Skands, P.Z. & /Fermilab
Partner: UNT Libraries Government Documents Department

BMSSM Higgs Bosons at the Tevatron and the LHC

Description: We study extensions of the Minimal Supersymmetric Standard Model (MSSM) with new degrees of freedom that couple sizably to the MSSM Higgs sector and lie in the TeV range. After integrating out the physics at the TeV scale, the resulting Higgs spectrum can significantly differ from typical supersymmetric scenarios, thereby providing a window Beyond the MSSM (BMSSM). Taking into account current LEP and Tevatron constraints, we perform an in-depth analysis of the Higgs collider phenomenology and explore distinctive characteristics of our scenario with respect to both the Standard Model and the MSSM. We propose benchmark scenarios to illustrate specific features of BMSSM Higgs searches at the Tevatron and the LHC.
Date: May 1, 2010
Creator: Carena, Marcela; /Fermilab /Chicago U., EFI; Ponton, Eduardo; U., /Columbia; Zurita, Jose & U., /Zurich
Partner: UNT Libraries Government Documents Department

Examining the identity of Yukawa with gauge couplings in supersymmetric QCD at LHC

Description: The identity of the quark-squark-gluino Yukawa coupling with the corresponding quark-quark-gluon QCD coupling in supersymmetric theories can be examined experimentally at the Large Hadron Collider (LHC). Extending earlier investigations of like-sign di-lepton final states, we include jets in the analysis of the minimal supersymmetric standard model, adding squark-gluino and gluino-pair production to squark-pair production. Moreover we expand the method towards model-independent analyses which cover more general scenarios. In all cases, squark decays to light charginos and neutralinos persist to play a dominant role.
Date: March 1, 2007
Creator: Freitas, Ayres; U., /Zurich; Skands, Peter Z.; /Fermilab; Spira, M.; /PSI, Villigen et al.
Partner: UNT Libraries Government Documents Department

Precision measurement of a particle mass at the linear collider

Description: Precision measurement of the stop mass at the ILC is done in a method based on cross-sections measurements at two different center-of-mass energies. This allows to minimize both the statistical and systematic errors. In the framework of the MSSM, a light stop, compatible with electro-weak baryogenesis, is studied in its decay into a charm jet and neutralino, the Lightest Supersymmetric Particle (LSP), as a candidate of dark matter. This takes place for a small stop-neutralino mass difference.
Date: June 1, 2007
Creator: Milstene, C.; /Fermilab; Freitas, A.; U., /Zurich; Schmitt, M.; U., /Northwestern et al.
Partner: UNT Libraries Government Documents Department

Search for Axions with the CDMS Experiment

Description: We report on the first axion search results from the Cryogenic Dark Matter Search (CDMS) experiment at the Soudan Underground Laboratory. An energy threshold of 2 keV for electron-recoil events allows a search for possible solar axion conversion into photons or local Galactic axion conversion into electrons in the germanium crystal detectors. The solar axion search sets an upper limit on the Primakov coupling g{sub a{gamma}{gamma}} of 2.4 x 10{sup ?9} GeV{sup -1} at the 95% confidence level for an axion mass less than 0.1 keV/c{sup 2}. This limit benefits from the first precise measurement of the absolute crystal plane orientations in this type of experiment. The Galactic axion search analysis sets a world-leading experimental upper limit on the axio-electric coupling g{sub a{bar e}e} of 1.4 x 10{sup -12} at the 90% confidence level for an axion mass of 2.5 keV/c{sup 2}. This analysis excludes an interpretation of the DAMA annual modulation result in terms of Galactic axion interactions for axion masses above 1.4 keV/c{sup 2}.
Date: February 1, 2009
Creator: Ahmed, Z.; /Caltech; Akerib, D.S.; U., /Case Western Reserve; Arrenberg, S.; U., /Zurich et al.
Partner: UNT Libraries Government Documents Department

Results from a Low-Energy Analysis of the CDMS II Germanium Data

Description: We report results from a reanalysis of data from the Cryogenic Dark Matter Search (CDMS II) experiment at the Soudan Underground Laboratory. Data taken between October 2006 and September 2008 using eight germanium detectors are reanalyzed with a lowered, 2 keV recoil-energy threshold, to give increased sensitivity to interactions from Weakly Interacting Massive Particles (WIMPs) with masses below {approx}10 GeV/c{sup 2}. This analysis provides stronger constraints than previous CDMS II results for WIMP masses below 9 GeV/c{sup 2} and excludes parameter space associated with possible low-mass WIMP signals from the DAMA/LIBRA and CoGeNT experiments.
Date: November 1, 2010
Creator: Ahmed, Z.; /Caltech; Akerib, D.S.; U., /Case Western Reserve; Arrenberg, S.; U., /Zurich-Irchel et al.
Partner: UNT Libraries Government Documents Department

Results from the Final Exposure of the CDMS II Experiment

Description: We report results from a blind analysis of the final data taken with the Cryogenic Dark Matter Search experiment (CDMS II) at the Soudan Underground Laboratory, Minnesota, USA. A total raw exposure of 612 kg-days was analyzed for this work. We observed two events in the signal region; based on our background estimate, the probability of observing two or more background events is 23%. These data set an upper limit on the Weakly Interacting Massive Particle (WIMP)-nucleon elastic-scattering spin-independent cross-section of 7.0 x 10{sup -44} cm{sup 2} for a WIMP of mass 70 GeV/c{sup 2} at the 90% confidence level. Combining this result with all previous CDMS II data gives an upper limit on the WIMP-nucleon spin-independent cross-section of 3.8 x 10{sup -44} cm{sup 2} for a WIMP of mass 70 GeV/c{sup 2}. We also exclude new parameter space in recently proposed inelastic dark matter models.
Date: December 1, 2009
Creator: Ahmed, Z.; /Caltech; Akerib, D.S.; U., /Case Western Reserve; Arrenberg, S.; U., /Zurich-Irchel et al.
Partner: UNT Libraries Government Documents Department

E.M. and Hadronic Shower Simulation with FLUKA

Description: A description of the main features of e.m. and hadronic shower simulation models used in the FLUKA code is summarized and some recent applications are discussed. The general status of the FLUKA project is also reported.
Date: October 3, 2005
Creator: Battistoni, G.; Fasso, A.; Ferrari, A.; Ranft, J.; Rubbia, A.; Sala, P.R. et al.
Partner: UNT Libraries Government Documents Department

The light stop quark with small stop-neutralino difference in the MSSM

Description: The MSSM can explain electro-weak symmetry breaking if one scalar top quark (stop) is light. In addition, in this framework, the neutralino is a good dark matter candidate and for small stop-neutralino mass differences dm{sub i} = 30 GeV, co-annihilation plays an important role to match the results from WMAP and SDSS for the relic density in the universe. In this scenario, the stops mainly decays into charm and neutralino, making its discovery difficult at hadron colliders due to background and trigger limitations. They present results for the discovery reach of the ILC for a DM candidate as low as 0(5 GeV) based on a realistic experimental simulation. Moreover, the stop parameters could be measured with high precision.
Date: December 1, 2005
Creator: Milstene, C.; Carena, M.; /Fermilab; Freitas, A.; U., /Zurich; Finch, A. et al.
Partner: UNT Libraries Government Documents Department

Hadronic Final States and QCD: Summary

Description: A summary of new experimental results and recent theoretical developments discussed in the 'Hadronic Final States and QCD' working group is presented.
Date: August 1, 2008
Creator: Gehrmann, Thomas; U., /Zurich; Grindhammer, Guenter; /Munich, Max Planck Inst.; O'Dell, Vivian; /Fermilab et al.
Partner: UNT Libraries Government Documents Department

Kaluza-Klein Dark Matter: Direct Detection vis-a-vis LHC

Description: We explore the phenomenology of Kaluza-Klein (KK) dark matter in very general models with universal extra dimensions (UEDs), emphasizing the complementarity between high-energy colliders and dark matter direct detection experiments. In models with relatively small mass splittings between the dark matter candidate and the rest of the (colored) spectrum, the collider sensitivity is diminished, but direct detection rates are enhanced. UEDs provide a natural framework for such mass degeneracies. We consider both 5-dimensional and 6-dimensional non-minimal UED models, and discuss the detection prospects for various KK dark matter candidates: the KK photon {gamma}{sub 1} (5D) the KK Z-boson Z{sub 1} (5D) and the spinless KK photon {gamma}{sub H} (6D). We combine collider limits such as electroweak precision data and expected LHC reach, with cosmological constraints from WMAP and the sensitivity of current or planned direct detection experiments. Allowing for general mass splittings, we show that neither colliders, nor direct detection experiments by themselves can explore all of the relevant KK dark matter parameter space. Nevertheless, they probe different parameter space regions and the combination of the two types of constraints can be quite powerful. For example, in the case of {gamma}{sub 1} in 5D UEDs the relevant parameter space will be almost completely covered by the combined LHC and direct detection sensitivities expected in the near future.
Date: November 1, 2008
Creator: Arrenberg, Sebastian; Baudis, Laura; U., /Zurich; Kong, Kyoungchul; /Fermilab; Matchev, Konstantin T. et al.
Partner: UNT Libraries Government Documents Department

Results from irradiation tests on D0 Run 2a silicon detectors at the Radiation Damage Facility at Fermilab

Description: Several different spare modules of the D0 experiment Silicon Microstrip Tracker (SMT) have been irradiated at the Fermilab Booster Radiation Damage Facility (RDF). The total dose received was 2.1 MRads with a proton flux of {approx} 3 {center_dot} 10{sup 11} p/cm{sup 2} sec. The irradiation was carried out in steps of 0.3 or 0.6 MRad, with several days between the steps to allow for annealing and measurements. The leakage currents and depletion voltages of the devices increased with dose, as expected from bulk radiation damage. The double sided, double metal devices showed worse degradation than the less complex detectors.
Date: March 1, 2006
Creator: Gardner, J.; Cerber, C.; Ke, Z.; Korjanevsky, S.; Leflat, A.; Lehner, F. et al.
Partner: UNT Libraries Government Documents Department

A low-threshold analysis of CDMS shallow-site data

Description: Data taken during the final shallow-site run of the first tower of the Cryogenic Dark Matter Search (CDMS II) detectors have been reanalyzed with improved sensitivity to small energy depositions. Four {approx}224 g germanium and two {approx}105 g silicon detectors were operated at the Stanford Underground Facility (SUF) between December 2001 and June 2002, yielding 118 live days of raw exposure. Three of the germanium and both silicon detectors were analyzed with a new low-threshold technique, making it possible to lower the germanium and silicon analysis thresholds down to the actual trigger thresholds of {approx}1 keV and {approx}2 keV, respectively. Limits on the spin-independent cross section for weakly interacting massive particles (WIMPs) to elastically scatter from nuclei based on these data exclude interesting parameter space for WIMPs with masses below 9 GeV/c{sup 2}. Under standard halo assumptions, these data partially exclude parameter space favored by interpretations of the DAMA/LIBRA and CoGeNT experiments data as WIMP signals, and exclude new parameter space for WIMP masses between 3 GeV/c{sup 2} and 4 GeV/c{sup 2}.
Date: October 1, 2010
Creator: Akerib, D.S.; U., /Case Western Reserve; Attisha, M.J.; U., /Brown; Baudis, L.; U., /Zurich-Irchel et al.
Partner: UNT Libraries Government Documents Department