4,485 research outputs found

    Inelastic Dark Matter and the SABRE Experiment

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    We present here the sensitivity of the SABRE (Sodium iodide with Active Background REjection) experiment to benchmark proto-philic, spin dependent, Inelastic Dark Matter models previously proposed due to their lowered tension with existing experimental results. We perform fits to cross section, mass, and mass splitting values to find the best fit to DAMA/LIBRA data for these models. In this analysis, we consider the Standard Halo Model (SHM), as well as an interesting extension upon it, the SHM+Stream distribution, to investigate the influence of the Dark Matter velocity distribution upon experimental sensitivity and whether or not its consideration may be able to help relieve the present experimental tension. Based on our analysis, SABRE should be sensitive to all the three benchmark models within 3-5 years of data taking.Comment: Adjusted for full DAMA run 1+2 efficiency. Updated to match published versio

    Probing new physics in electroweak penguins through B_d and B_s decays

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    An enhanced electroweak penguin amplitude due to the presence of unknown new physics can explain the discrepancies found between theory and experiment in the B -> pi K decays, in particular in A_CP(B^- -> pi^0 K^-) - A_CP(\bar{B}^0 -> pi^+ K^-), but the current precision of the theoretical and experimental results does not allow to draw a firm conclusion. We argue that the \bar{B}_s -> phi rho^0 and \bar{B}_s -> phi pi^0 decays offer an additional tool to investigate this possibility. These purely isospin-violating decays are dominated by electroweak penguins and we show that in presence of a new physics contribution their branching ratio can be enhanced by about an order of magnitude, without violating any constraints from other hadronic B decays. This makes them very interesting modes for LHCb and future B factories. In arXiv:1011.6319 we have performed both a model-independent analysis and a study within realistic New Physics models such as a modified-Z^0-penguin scenario, a model with an additional Z' boson and the MSSM. In this article we summarise the most important results of our study.Comment: 8 pages, 5 figures, LaTeX. Talk given at Discrete2010, Rome, 6-11 December 2010; References adde

    Why do we need higher order fully exclusive Monte Carlo generator for Higgs boson production from heavy quark fusion at LHC?

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    In this paper we argue that having available higher order fully exclusive Monte Carlo generator for Higgs boson production from heavy quark fusion will be mandatory for data analysis at LHC. The H to tau tau channel, a key for early discovery of the Higgs boson in the MSSM scenario, is discussed. With simplified example and for mH = 120 GeV we show, that depending on choice among presently available approaches, used for simulation of Higgs boson production from b bbar H Yukawa coupling, final acceptance for the signal events being reconstructed inside mass window may differ by a factor of 3. The spread is even larger (up to a factor of 10) for other production mechanisms (promising for some regions of the MSSM parameter space). The complete analysis, which necessarily will add stringent requirements for background rejection (such as identification of b-jet or veto on b-jet) and which will require statistical combination of samples selected with different selection criteria may only enhance the uncertainty.Comment: 14 pages, 22 figure

    CP asymmetries at D0

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    Using two independent measurements of the semileptonic CP asymmetry in the BsB_s system, we constrain the CP violating phase of the BsB_s system to be ϕs=0.700.39+0.47\phi_s = -0.70^{+0.47}_{-0.39}. The data sample corresponds to an integrated luminosity of 1.1 fb1^{-1} accumulated with D0 detector at the Fermilab Tevatron collider. We also measure the direct CP violating asymmetry in the decay B+J/ψK+B^+ \to J/\psi K^+ to be ACP(B+J/ψK+)=+0.0067±0.0074A_{CP}(B^+ \to J/\psi K^+) = +0.0067 \pm 0.0074(stat)±0.0026\pm0.0026(syst). The data corresponds to an integrated luminosity of 1.6 fb1^{-1}.Comment: contributed paper to EPS07, Manchester, UK, manuscript number EPSHEPP17

    QCD Approach to B->D \pi Decays and CP Violation

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    The branching ratios and CP violations of the BDπB\to D\pi decays, including both the color-allowed and the color-suppressed modes, are investigated in detail within QCD framework by considering all diagrams which lead to three effective currents of two quarks. An intrinsic mass scale as a dynamical gluon mass is introduced to treat the infrared divergence caused by the soft collinear approximation in the endpoint regions, and the Cutkosky rule is adopted to deal with a physical-region singularity of the on mass-shell quark propagators. When the dynamical gluon mass μg\mu_g is regarded as a universal scale, it is extracted to be around μg=440\mu_g = 440 MeV from one of the well-measured BDπB\to D\pi decay modes. The resulting predictions for all branching ratios are in agreement with the current experimental measurements. As these decays have no penguin contributions, there are no direct CPCP asymmetries. Due to interference between the Cabibbo-suppressed and the Cabibbo-favored amplitudes, mixing-induced CP violations are predicted in the BD±πB\to D^{\pm}\pi^{\mp} decays to be consistent with the experimental data at 1-σ\sigma level. More precise measurements will be helpful to extract weak angle 2β+γ2\beta+\gamma.Comment: 21pages,5 figures,3 tables, typos corrected and numerical result for one of decay channels is improve

    CPV tests with rare kaon decays

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    The K_S \to pi+/- e+ e- decay mode has been investigated using the data collected in 2002 by the NA48/1 collaboration. With about 23k signal events and 59k K_L \to pi+ pi- pi0_D normalization decays, the K_S \to pi+ pi- e+ e- branching ratio was determined. This result is also used to set an upper limit on the presence of E1 direct emission in the decay amplitude. The CP-violating asymmetry has been also measured. We report on measurements of the rare decays K +/- \to pi+/- e+ e- and K+/- \to pi+/- mu+ mu- . The full NA48/2 data set was analyzed, leading to more than 7200 reconstructed events in the electronic and more than 3000 events in the muonic channel, the latter exceeding the total existing statistics by a factor of four. For both channels the selected events are almost background-free. From these events, we have determined the branching fraction and form factors of K+/- \to pi+/- e+ e- using different theoretical models. Our results improve the existing world averages significantly. In addition, we measured the CP violating asymmetry between K+ and K- in this channel to be less than a few percent.Comment: 4 pages, 1 figure, To appear in the proceedings of IX International Conference on Hyperons, Charm and Beauty Hadrons (BEACH2010), Perugia, Italy, 21-26 June 201

    Bremsstrahlung simulation in K to pi l^pm nu_l (gamma) decays

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    In physics simulation chains, the PHOTOS Monte Carlo program is often used to simulate QED effects in decays of intermediate particles and resonances. The program is based on an exact multiphoton phase space. In general, the matrix element is obtained from iterations of a universal kernel and approximations are involved. To evaluate the program precision, it is necessary to formulate and implement within the generator the exact matrix element, which depends on the decay channel. Then, all terms necessary for non-leading logarithms are taken into account. In the present letter we focus on the decay K to pi l^pm nu_l and tests of the PHOTOS Monte Carlo program. We conclude a 0.2% relative precision in the implementation of the hard photon matrix element into the emission kernel, including the case where approximations are used.Comment: 1+20 pages, 8 figure

    Analysis of Ba1(1260)(b1(1235))KB \to a_1(1260)(b_1(1235))K^* decays in the perturbative QCD approach

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    Within the framework of perturbative QCD approach, we study the charmless two-body decays Ba1(1260)K,b1(1235)KB\to a_1(1260)K^*, b_1(1235)K^*. Using the decays constants and the light-cone distribution amplitudes for these mesons derived from the QCD sum rule method, we find the following results: (a) Our predictions for the branching ratios are consistent well with the QCDF results within errors, but much larger than the naive factorization approach calculation values. (b) We predict that the anomalous polarizations occurring in the decays BϕK,ρKB\to \phi K^*, \rho K^* also happen in the decays Ba1KB\to a_1K^*, while do not happen in the decays Bb1KB\to b_1K^*. Here the contributions from the annihilation diagrams play an important role to explain the lager transverse polarizations in the decays Ba1KB\to a_1K^*, while they are not sensitive to the polarizations in decays Bb1KB\to b_1K^*. (c) Our predictions for the direct CP-asymmetries agree well with the QCDF results within errors. The decays Bˉ0b1+K,Bb10K\bar B^0\to b^{+}_1K^{*-}, B^-\to b^{0}_1K^{*-} have larger direct CP-asymmetries, which could be measured by the present LHCb experiments.Comment: 12pages, 1figures. arXiv admin note: substantial text overlap with arXiv:1203.5913, arXiv:1203.591
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