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.
118555858
Enriching the exploration of the mUED model with event shape variables at the CERN LHC
Abstract We propose a new search strategy based on the event shape variables for new physics models where the separations among the masses of the particles in the spectrum are small. Collider signature of these models, characterized by low p T leptons/jets and low missing p T , are known to be difficult to look for. The conventional search strategies involving hard cuts may not work in such situations. As a case study, we have investigated the hitherto neglected jets + missing E T signature – known to be a challenging one – arising from the pair productions and decay of n = 1 KK-excitations of gluons and quarks in the minimal Universal Extra Dimension (mUED) model. Judicious use of the event shape variables enables us to reduce the Standard Model backgrounds to a negligible level. We have shown that in mUED, R − 1 up to 850 GeV can be explored or ruled out with 12 fb −1 of integrated luminosity at the 7 TeV run of the LHC. We also discuss the prospects of employing these variables for searching other beyond Standard Model physics with compressed or partially compressed spectra.
118117079
Mutual consistency of the MINOS and MiniBooNE Antineutrino Results and Possible CPT Violation
Discussing the recent MINOS data on muon anti-neutrino disappearance and the MiniBooNE data on muon anti-neutrino to electron anti-neutrino oscillation, we show that the while the respective best fits are inconsistent with each other, significant overlap of allowed regions does exist. Assuming only three neutrino species, the data indicates a discrepancy of mass levels and mixing angles between the neutrino and the antineutrino sectors. We show that the existing data can be reconciled with a model of explicit CPT violation in the neutrino sector and estimate the magnitude of the required violation.
14197025
More on Violation of Angular-Momentum Selection Rules in Quantum Gravity
In a recent paper, we noticed that, in the s-channel scattering mediated by a graviton in the linearized Einstein theory, angular momentum seems not to be conserved in the graviton coupling to massive matter fields, due to the presence of a scalar component in the partial-wave expansion of the relevant amplitudes. The present Letter answers to some criticism by Han and Willenbrock, claiming that there is no problem in propagating a scalar component through a graviton exchange. We show explicitly that the partial-wave decomposition of the scattering amplitude contrasts with the rotation-group representations propagating through the graviton exchange in the considered processes. This phenomenon is crucially connected to the critical dependence of the trace of the graviton propagator on the effective dimension of the problem. In a recent work [1], we showed that angular-momentum selection rules are violated in the linearized limit of quantum gravity in the Einstein theory. In particular, we considered the scattering amplitudes of either massive fermion or massive gauge-boson pairs mediated by a graviton in the s-channel, and computed their non vanishing interferences with the amplitudes where a scalar field replaces the graviton. Since in the s-channel scattering of real particles only graviton components of angular momentum J = 2 propagate [2], a non vanishing interference with the scalar (J = 0) exchange 1 amplitude seems to point to a violation of the angular-momentum conservation in the graviton-matter vertex. Our statement was not based on special assumptions. It was derived in a straightforward way from the Feynman rules of the Einstein theory minimally coupled to massive fermion and vector-boson fields. In a following paper by Han and Willenbrock [3], it has been argued that our conclusion would be incorrect, since it is based on the wrong assumption that no J = 0 component is exchanged in the graviton propagator. The authors stress that in the s-channel amplitude mediated by a graviton, also an SO(3, 1) scalar component can propagate. The latter couples to the trace of the energy momentum tensor of the matter fields Tμν (that is non vanishing for massive fields). They conclude that there is no violation of angular-momentum selection rules in quantum gravity. In our paper [1], the crucial statement that only J = 2 graviton components contribute to the considered amplitudes was based on a previous work by van Dam and Veltman [2], and was not proved explicitly. The purpose of the present Letter is to clarify this issue, by showing that there are processes where there is a J = 0 component in the partial-wave decomposition of the s-channel amplitude, and, on the other hand, no J = 0 component propagates in the virtual graviton state. This fact will be shown to be crucially connected to the critical dependence of the trace of the graviton propagator tensor on the effective dimension of the analyzed problem. Let us consider the general form of the graviton propagator in the linearized Einstein theory. When contracted with conserved energy momentum tensors (i.e., for qμTμν = 0, with qμ the momentum flowing in the propagator), terms proportional to the momentum are not relevant, and the effective massless graviton propagator becomes∗ Gμναβ(q) = i Pμναβ q2 + iǫ ; Pμναβ = 1 2 (ημαηνβ + ημβηνα − ημνηαβ) , (1) The s-channel p1p1 → p2p2 scattering amplitude mediated by a graviton is then given by A = −i M P ( T f† μν Gμναβ(q) T i αβ ) (2) where T i(f) μν are the matrix elements of the conserved energy momentum tensor of the initial (final) states, and MP is the Planck mass. In this Letter, indices (μ, ν, α, β) are contracted according to the Minkowski metric ημν = Diag(1,−1,−1,−1).
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.
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.
118310374
Probing New Physics in Higgs Couplings to Fermions using an Angular Analysis
The standard-model Higgs boson couples to quarks through a parity-even scalar Hqcou- pling. We show that the rare Higgs decay H ! V Z, where V is a vector quarkonium state such as J/ψ (c¯) or �(1S) (bb), can be used to search for the presence of a parity-odd pseudoscalar Hq¯ q coupling. Since both V and Z can decay to a pair of charged leptons, this presents an experimentally-clean channel that can be observed at the high-luminosity LHC or a future hadron collider. The P-even and P-odd Hqcouplings can be measured by analyzing the angular distribution of the final-state leptons.
118959585
Deviation from Tri-Bimaximal Neutrino mixing from the Charged Lepton Sector
The tri-bimaximal mixing matrix is most likely the leading order term in the description of leptonic mixing. We derive deviations from tri-bimaximal mixing(TBM) due to corrections from the charged lepton sector. We assume a decoupled 2-3 symmetry, which is a $Z_2$ symmetry, in the charged lepton sector and another $Z_2$ symmetry in the neutrino sector. The TBM is obtained in the flavor symmetric limit. We consider deviations from the TBM form arising from the breaking of the 2-3 symmetry in the charged lepton sector but do not consider deviations from the breaking of the flavor symmetry in the neutrino sector. In particular we find the size of $\sin{\theta_{13}}$ to be related to the deviation $\sin{\theta_{12}}$ from $\sqrt{1/3}$ while the deviation of $\sin{\theta_{23}}$ from its tri-bimaximal value is $ \sim {m_{\mu} \over m_{\tau}}$.
119120552
Tau-neutrino as a probe of nonstandard interaction
Abstract We study the Δ-resonance and deep inelastic scattering contributions in the tau-neutrino–nucleon scattering ν τ + N → τ − + X and ν ¯ τ + N → τ + + X in the presence of a charged Higgs and a W ′ gauge boson. The new physics effects to the quasielastic process have been discussed in a previous work. The extractions of the atmospheric mixing angle θ 23 rely on the standard model cross sections for ν τ + N → τ − + X in ν τ appearance experiments. Corrections to the cross sections from the charged Higgs and W ′ contributions modify the measured mixing angle. We include form factor effects in the new physics calculations and find the deviations of the mixing angle. If high-energy Long Base Line experiments are designed to measure θ 13 through tau-neutrino appearance, the new physics effects to ν τ + N → τ − + X and ν ¯ τ + N → τ + + X can impact the extraction of this mixing angle. Finally, we investigate the new physics effects on the polarization of the τ ∓ leptons produced in ν τ ( ν ¯ τ ) –nucleon scattering.
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.
120953992
New physics in b --> smu + mu -: CP-violating observables