1534033
Probing two universal extra dimensions at international linear collider
Abstract We discuss collider signatures of ( 1 , 1 ) th Kaluza–Klein (KK) mode vector bosons in the framework of two universal extra dimension model, at a future e + e − collider. Production of B μ ( 1 , 1 ) and W 3 μ ( 1 , 1 ) , the ( 1 , 1 ) th KK mode vector bosons, are considered in association with a hard photon. Without caring about the decay products of B μ ( 1 , 1 ) or W 3 μ ( 1 , 1 ) , one can measure the masses of these particles just by looking at the photon energy distribution. Once produced B μ ( 1 , 1 ) ( W 3 μ ( 1 , 1 ) ) dominantly decays to a pair of jets or to a pair of top quarks. Thus we look for a pair of jets or a pair of top quarks in association with a photon. Upto the kinematic limit (with e + e − center-of-mass energies of 0.5 TeV and 1 TeV) of the collider, signals from the B μ ( 1 , 1 ) production and decay in both the above mentioned channels are greater than the 5σ fluctuation of the Standard Model background with 500 f b −1 integrated luminosity. However, the number of events from W 3 μ ( 1 , 1 ) production and decay is smaller and its detection prospect is not very good.
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.
15877
Invisible Higgs in theories of large extra dimensions
We discuss the possibility of detecting a Higgs boson in future collider experiments if large extra dimensions are realized in nature. In such a case, the Higgs boson can decay invisibly by oscillating into a graviscalar Kaluza-Klein (KK) tower. We show that the search for such a Higgs at an ee linear collider entails more complications than are usually thought of in relation to an invisibly decaying Higgs, the main sources of such complications being the simultaneous presence of a continuum graviton production and the broadening of the Higgs peak. We discuss possible ways of overcoming such difficulties, and conclude that the detection of such a Higgs boson might still be a problem beyond the mass range of 250-300 GeV.
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.
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.
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.
118071488
Single Top Production and Extra Dimensions
In extra dimension theories, where the gauge bosons of the standard model propagate in the bulk of the extra dimensions, there are Kaluza‐Klein excitations of the standard model gauge bosons that can couple to the standard model fermions. In this paper we study the effects of the excited Kaluza‐Klein modes of the W on single top production at the Tevatron.
17434465
HADRONIC B DECAYS: A GENERAL APPROACH
In this paper, we propose a general approach for describing hadronic B decays. Using this method, all amplitudes for such decays can be expressed in terms of contractions, though the matrix elements are not evaluated. Many years ago, Buras and Silvestrini proposed a similar approach. However, our technique goes beyond theirs in several ways. First, we include recent theoretical and experimental developments which indicate which contractions are negligible, and which are expected to be smaller than others. Second, we show that all B-decay diagrams can be simply expressed in terms of contractions. This constitutes a formal proof that the diagrammatic method is rigorous. Third, we show that one reproduces the relations between tree and electroweak-penguin diagrams described by Neubert and Rosner, and by Gronau, Pirjol and Yan. Fourth, although the previous results hold to all orders in αs, we show that it is also possible to work order-by-order in this approach. In this way it is possible to make a connection with the matrix-element evaluation methods of QCD factorization (QCDfac) and perturbative QCD (pQCD). Finally, using the contractions approach, we reevaluate the question of whether there is a "B → πK puzzle." At , we find that the diagram ratio |C′/T′| is about 0.17, a factor of 10 too small to explain all the B → πK data. Both QCDfac and pQCD find that, at , the value of |C′/T′| may be raised to only about 2–3 times its lowest-order value. We therefore conclude that, assuming the effect is not a statistical fluctuation, it is likely that the value of |C′/T′| is similar to its result, and that there really is a B → πK puzzle.
18884350
Weak decays to final states with radial excitation admixtures
We consider the weak decays of a B meson to final states that are mixtures of S-wave radially excited components. We consider non leptonic decays of the type $B \to \rho' \pi/B \to \rho \pi$, $B \to \omega' \pi/B \to \omega \pi$ and $B \to \phi' \pi/B \to \phi \pi$ where $\rho'$, $\omega'$ and $\phi'$ are higher $\rho$, $\omega$ and $\phi$ resonances. We find such decays to have larger or similar branching ratios compared to decays where the final state $\rho$, $\omega$ and $\phi$ are in the ground state. We also study the effect of radial mixing in the vector and the pseudoscalar systems generated from hyperfine interaction and the annihilation term. We find the effects of radial mixing to be small and generally negligible for all practical purposes in the vector system. However, in the $\eta-\eta^{\prime}$ system the effects of radial mixing are appreciable and seriously affect decay branching ratios for $B \to \eta(\eta')K(K^*)$. In particular we find that nonstandard $\eta(\eta')$ mixing can resolve the puzzles in $B \to \eta(\eta')K$ decays.
17105922
Effects of Kaluza-Klein excited W on single top quark production at the Tevatron
In extra dimension theories if the gauge bosons of the standard model propagate in the bulk of the extra dimensions then they will have Kaluza-Klein excitations that can couple to the standard model fermions. In this paper we study the effects of the first excited Kaluza-Klein mode of the W on single top production at the Tevatron. We find that the cross section for the single top production can be significantly reduced if the mass of the first Kaluza-Klein excited W similar to 1 TeV. Hence, a measurement of the single top production cross section smaller than the standard model prediction would not necessarily imply V-tb < 1 or evidence of extra generation(s) of Fermions mixed with the third generation. (C) 2000 Elsevier Science B.V. All rights reserved.
204935588
Measuring beta in B ---> D(*)+ D(*)- K(s) decays
We consider the possibility of measuring both $\sin (2 \beta)$ and $\cos (2 \beta)$ in the KM unitarity triangle using the process $B^0 \to D^{*+}D^{*-}K_s$. This decay mode has a higher branching fraction (O(1%)) than the mode $B^0 \to D^{*+}D^{*-}$. We use the factorization assumption and heavy hadron chiral perturbation theory to estimate the branching fraction and polarization. The time dependent rate for $B^0(t) \to D^{*+} D^{*-} K_s$ can be used to measure $\sin (2 \beta)$ and $\cos(2 \beta)$ . Furthermore, examination of the $D^{*+} K_s$ mass spectrum may be the best way to experimentally find the broad $1^+$ p-wave $D_s$ meson.