125209638
What does the mu(nu) oscillate into
118278744
Higgs Boson Signals in Three b-jet Final States at the Fermilab Tevatron
At the Fermilab Tevatron, final states with three tagged b-jets could play an important role in searches for a Higgs boson with mass in the range 100-300 GeV. These signals arise from gb fusion and we demonstrate their observability in the limit of a large b-quark Yukawa coupling. Rather promising discovery limits on such a coupling are obtained and consequent effects on the parameter space of the Higgs-boson sector in the MSSM are discussed.
54016829
Deciphering universal extra dimension from the top quark signals at the CERN LHC
Models based on Universal Extra Dimensions predict Kaluza-Klein (KK) excitations of all Standard Model (SM) particles. We examine the pair production of KK excitations of top- and bottom-quarks at the Large Hadron Collider. Once produced, the KK top/bottom quarks can decay to b-quarks, leptons and the lightest KK-particle, γ1, resulting in 2 b-jets, two opposite sign leptons and missing transverse momentum, thereby mimicing top-pair production. We show that, with a proper choice of kinematic cuts, an integrated luminosity of 100 fb−1 would allow a discovery for an inverse radius upto R−1 = 750GeV.
657627
Virtual graviton exchanges at the Z pole in large extra dimensions
Abstract In the framework of quantum gravity propagating in large extra dimensions, the effects of virtual Kaluza–Klein gravitons on the imaginary part of the amplitude of the process e + e − →f f are analyzed at the Z pole. Notably, the interference of the almost-continuous spectrum of the KK gravitons with the standard model resonant amplitude is finite and predictable in terms of the fundamental D-dimensional Planck scale MD. We find that, while the virtual-graviton effect on total cross sections vanishes at tree-level, both angular and polarization asymmetries are modified by terms whose relative effect is at most of order 10−4 for MD>1 TeV. Possible shifts in MZ, due to the changes in Breit–Wigner line shape are also discussed.
17475961
ZZH coupling: a probe to the origin of EWSB?
Abstract We argue that the ZZH coupling constitutes a simple probe of the nature of the scalar sector responsible for electroweak symmetry breaking. We demonstrate the efficacy of this measure through an analysis of four-dimensional models containing scalars in arbitrary representation of SU (2)× U (1), as well as extra-dimensional models with a non-factorizable geometry. A possible role for the t t H couplings is also discussed.
119099061
Probing the violation of equivalence principle at a muon storage ring via neutrino oscillation
Abstract We examine the possible tests of violation of the gravitational equivalence principle (VEP) at a muon storage ring via neutrino oscillation experiments. If the gravitational interactions of the neutrinos are not diagonal in the flavour basis and the gravitational interaction eigenstates have different couplings to the gravitational field, this leads to the neutrino oscillation. If one starts with μ + beam then appearance of τ ± , e + and μ − in the final state are the signals for neutrino oscillation. We have estimated the number of μ − events in this scenario in ν μ – N deep inelastic scattering. Final state lepton energy distribution can be used to distinguish the VEP scenario from the others. A large area of VEP parameter space can be explored at a future muon storage ring facility with moderate beam energy.
118496504
Model independent predictions for rare top decays with weak coupling
Measurements at B factories have provided important constraints on new physics in several rare processes involving the B meson. New physics, if present in the b quark sector may also affect the top sector. In an effective Lagrangian approach, we write down operators, where effects in the bottom and the top sector are related. Assuming the couplings of the operators to be of the same size as the weak coupling g of the standard model and taking into account constraints on new physics from the bottom sector as well as top branching ratios, we make predictions for the rare top decays t{yields}cV, where V={gamma}, Z. We find branching fractions for these decays within possible reach of the LHC. Predictions are also made for t{yields}sW.
118836250
Diagnosing New Physics in $B \to C \, \tau \, \nu_\tau$ Decays in the Light of the Recent BaBar Result
The BaBar Collaboration has recently reported the measurement of the ratio of the branching fractions of $\bar{B} \to D(D^{*}) \tau^{-} \bar{\nu_\tau}$ to $\bar{B} \to D(D^{*}) \ell^{-} \bar{\nu_\ell}$ which deviates from the Standard Model prediction by 2$\sigma$(2.7$\sigma$). This deviation goes up to 3.4$\sigma$ level when the two measurements in the $D$ and $D^*$ modes are taken together and could indicate new physics. Using an effective Lagrangian for the new physics we study the implication of these results and calculate other observables that can shed light on the nature of the new physics. We show that the measurements of the forward-backward asymmetries and the $\tau$ and $D^*$ polarization fractions can distinguish among the various couplings of the new physics operators.
42567676
Is there new physics in B decays
Rare decays of the B meson are sensitive to new physics effects. Several experimental results on these decays have been difficult to understand within the Standard Model (SM) though more precise measurements and a better understanding of SM theory predictions are needed before any firm conclusions can be drawn. In this note we try to understand the present data assuming the presence of new physics. We find that the data points to new physics of an extended Higgs sector and we present a two-Higgs-doublet model with a 2–3 flavor symmetry in the down-type quark sector that can explain the deviations from the Standard Model reported in several rare B decays. PACS Nos.: 11.30.Er, 11.30.Hv, and 13.20.He
118381371
Searching for new physics with B-decay fake triple products
Abstract In pure-penguin b ¯ → s ¯ B → V 1 V 2 decays ( V 1 , 2 are vector mesons), f T / f L ≃ 1 has been observed ( f T ( f L ) is the polarization fraction of transverse (longitudinal) decays). Explanations of this unexpectedly large result have been given within the standard model (SM) and with new physics (NP). In this Letter, we show that these two explanations can be partially distinguished through the triple products (TPʼs) in these transitions. In particular, the SM predicts one of the two fake, CP-conserving TPʼs to be small ( | A T ( 2 ) | ⩽ 9 % ), while NP often gives larger values for | A T ( 2 ) | . We discuss the implications of the measurements of both fake TPʼs in B → ϕ K ⁎ – the present data prefer an SM explanation of f T / f L – and provide the SM predictions for B s 0 → ϕ ϕ .
9738460
Obtaining CKM phase information from B penguin decays
We discuss a method for extracting CP phases from pairs of B decays which are related by flavor SU(3). One decay (B0→M1M2) receives a significant → penguin contribution. The second (B'→M'1M'2) has a significant → penguin contribution, but is dominated by a single amplitude. CP phase information is obtained using the fact that the B'→M'1M'2 amplitude is related by SU(3) to a piece of the B0→M1M2 amplitude. The leading-order SU(3)-breaking effect ( ~ 25%) responsible for the main theoretical error can be removed. For some decay pairs, it can be written in terms of known decay constants. In other cases, it involves a ratio of form factors. However, this form-factor ratio can either be measured experimentally, or eliminated by considering a double ratio of amplitudes. In all cases, one is left only with a second-order effect, ~ 5%. We find twelve pairs of B decays to which this method can be applied. Depending on the pair, we estimate the total theoretical error in relating the B'→M'1M'2 and B0→M1M2 amplitudes to be between 5% and 15%. The most promising decay pairs are Bd0→π+π− and Bu+→K0π+, and Bd0→D+D− and Bd0→Ds+D− or Bu+→Ds+0.