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Yuval Grossman

Publications and source records attributed to Yuval Grossman.

At least 127 records · Page 7Linked to original sources
arXiv2003

Measuring $γ$ in $B^\pm \to K^\pm (K K^*)_D$ decays

We develop a method to measure the CKM angle $γ$ without hadronic uncertainties from the analysis of $B^\pm \to K^\pm D^0$ and $K^\pm \D0bar$ followed by singly Cabibbo-suppressed $D$ decays to non CP-eigenstates, such as $K^\pm K^{*\mp}$. This method utilizes the interference between $b\to c\bar u s$ and $b\to u\bar c s$ decays, and we point out several attractive features of it. All the modes that need to be measured for this method are accessible in the present data.

hep-ph↗
arXiv2002

The would-be majoron in R-parity-violating supersymmetry

In lepton-number-violating supersymmetric models, there is no natural choice of basis to distinguish the down-type Higgs and lepton superfields. We employ basis-independent techniques to identify the massless majoron and associated light scalar in the case of spontaneously-broken lepton number (L). When explicit L-violation is added, these two scalars can acquire masses of order the electroweak scale and can be identified as massive sneutrinos.

hep-ph↗
arXiv2002

Realistic construction of split fermion models

The Standard Model flavor structure can be explained in theories where the fermions are localized on different points in a compact extra dimension. We show that models with two bulk scalars compactified on an orbifold can produce such separations in a natural way. We study the shapes and overlaps of the fermion wave functions. We show that, generically, realistic models of Gaussian overlaps are unnatural since they require very large Yukawa couplings between the fermions and the bulk scalars. We give an example of a five dimensional two scalar model that accounts naturally for the observed quark masses, mixing angles and CP violation.

hep-ph↗
arXiv2002

Effects of initial axion production and photon--axion oscillation on type Ia supernova dimming

Recently, Csaki, Kaloper and Terning (CKT) suggested that axion-photon oscillation in the intergalactic medium can explain the observed dimming of distant type Ia supernovae. This mechanism works only if the initial axion flux is much smaller than the initial photon flux. We study several mechanisms for such initial axion production. The direct axion production in the supernovae, the photon-axion oscillation in the magnetic field of supernovae and in the magnetic field of their host galaxies are addressed. We find it likely that the initial axion flux is very small and therefore does not pose a problem to the CKT mechanism.

hep-ph↗
arXiv2002

Can the CP asymmetries in $B\to ψK_S$ and $B\to ψK_L$ differ?

In the standard model the CP asymmetries in $B\to ψK_S$ and $B\to ψK_L$ are equal in magnitude and opposite in sign to very good approximation. We compute the order $ε_K$ corrections to each of these CP asymmetries and find that they give a deviation from $\sin 2β$ at the half percent level, which may eventually be measurable. However, the correction to $a_{CP}(B\to ψK_S)+a_{CP}(B\to ψK_L)$ due to $ε_K$ is further suppressed. The dominant corrections to this sum, at the few times $10^{-3}$ level, come from the $B$ lifetime difference, and CP violation in $B- \bar B$ mixing and $B \to ψK$ decay. New physics could induce a significant difference in the $\sin(Δm_B t)$ time dependence in the asymmetries if and only if the "wrong-flavor" amplitudes $B \to ψ\bar K$ or $\bar B \to ψK$ are generated. A scale of new physics that lies well below the weak scale would be required. Potential scenarios are therefore highly constrained, and do not appear feasible. A direct test is proposed to set bounds on such effects.

hep-ph↗
arXiv2001

Measuring the Photon Helicity in Radiative B Decays

We propose a way of measuring the photon polarization in radiative B decays into K resonance states decaying to Kππ, which can test the Standard Model and probe new physics. The photon polarization is shown to be measured by the up-down asymmetry of the photon direction relative to the Kππdecay plane in the K resonance rest frame. The integrated asymmetry in K_1(1400)\to Kππ, calculated to be 0.34\pm 0.05 in the Standard Model, is measurable at currently operating B factories.

hep-ph↗
arXiv2001

SU(3) Breaking and D0-D0bar Mixing

The main challenge in the Standard Model calculation of the mass and width difference in the D0-D0bar system is to estimate the size of SU(3) breaking effects. We prove that D meson mixing occurs in the Standard Model only at second order in SU(3) violation. We consider the possibility that phase space effects may be the dominant source of SU(3) breaking. We find that y=(Delta Gamma)/(2Gamma) of the order of one percent is natural in the Standard Model, potentially reducing the sensitivity to new physics of measurements of D meson mixing.

hep-ph↗
arXiv2001

Slepton Flavor Physics at Linear Colliders

If low energy supersymmetry is realized in nature it is possible that a first generation linear collider will only have access to some of the superpartners with electroweak quantum numbers. Among these, sleptons can provide sensitive probes for lepton flavor violation through potentially dramatic lepton violating signals. Theoretical proposals to understand the absence of low energy quark and lepton flavor changing neutral currents are surveyed and many are found to predict observable slepton flavor violating signals at linear colliders. The observation or absence of such sflavor violation will thus provide important indirect clues to very high energy physics. Previous analyses of slepton flavor oscillations are also extended to include the effects of finite width and mass differences.

hep-ph↗
arXiv2001

Measuring $D^0-\bar D^0$ Mixing and Relative Strong Phases at a Charm Factory

We propose a set of measurements at a charm factory to determine the $D^0-\bar D^0$ mixing parameters $ΔM$ and $ΔΓ$ and the strong phase difference $δ$ between doubly-Cabibbo-suppressed (DCS) and Cabibbo-favored (CF) neutral $D$ decays into $K^-π^+$. The method can also be used to measure strong phase differences between other corresponding DCS and CF amplitudes. These phase differences are important for studies of $D^0$--$\bar D^0$ mixing.

hep-ph↗
arXiv2000

Beyond the standard model with B physics

Extensions of the Standard Model may have significant effects on B physics observables. Two examples of methods that may find such effects are reviewed: Resolving discrete ambiguities in CP asymmetries and detecting right handed currents in radiative B decays.

hep-ph↗
arXiv2000

Basis-independent analysis of the sneutrino sector in R-parity violating supersymmetry

In R-parity-violating supersymmetric models (with a conserved baryon number), there are no quantum numbers that distinguish the lepton-doublet and down-type Higgs supermultiplets. As a result, the R-parity-violating parameters depend on the basis choice for these superfields, although physical observables are independent of the choice of basis. This paper presents a basis-independent computation of the sneutrino/antisneutrino squared-mass splitting in terms of basis-independent quantities. Techniques are developed for an arbitrary number of sneutrino generations; specific results are provided for the one, two and three generation cases.

hep-ph↗
arXiv2000

Extracting and using photon polarization information in radiative B decays

We discuss the uses of conversion electron pairs for extracting photon polarization information in weak radiative B decays. Both cases of leptons produced through a virtual and real photon are considered. Measurements of the angular correlation between the $(Kπ)$ and $(e^+e^-)$ decay planes in $B\to K^*(\to Kπ)γ^{(*)}(\to e^+e^-)$ decays can be used to determine the helicity amplitudes in the radiative $B\to K^*γ$ decay. A large right-handed helicity amplitude in $\bar B$ decays is a signal of new physics. The time-dependent CP asymmetry in the $B^0$ decay angular correlation is shown to measure $\sin 2β$ and $\cos 2β$ with little hadronic uncertainty.

hep-ph↗
arXiv2000

Lessons from CLEO and FOCUS Measurements of D0-anti-D0 Mixing Parameters

If the true values of the D0-anti-D0 mixing parameters lie within the one sigma ranges of recent measurements, then there is strong evidence for a large width difference, y > 0.01, and large SU(3) breaking effects in strong phases, δ> pi/4. These constraints are model independent, and would become stronger if M_{12}/Gamma_{12} << 1 in the D0-anti-D0 system. The interesting fact that the FOCUS result cannot be explained by a large mass difference is not trivial and depends on the small D0-anti-D0 production asymmetry in FOCUS and the bounds on CP violating effects from CLEO. The large value of δmight help explain why y ~ sin^2(theta_c).

hep-ph↗
arXiv2000

Experimental Signatures of Split Fermions in Extra Dimensions

The smallness and hierarchy of the fermion parameters could be explained in theories with extra dimensions where doublets and singlets are localized at slightly separated points. Scattering cross sections for collisions of such fermions vanish exponentially at energies high enough to probe the separation distance. This is because the separation puts a lower bound on the attainable impact parameter in the collision. The NLC, and in particular the combination of the e^+e^- and e^-e^- modes, can probe this scenario, even if the inverse fermion separation is of order tens of TeVs.

hep-ph↗
arXiv2000

Neutrino masses and mixings in non-factorizable geometry

We study bulk fermion fields in the localized gravity model with non-factorizable metric recently proposed by Randall and Sundrum, and Gogberashvili. In addition to a tower of weak-scale Kaluza-Klein states we find a zero mode for any value of the fundamental fermion mass. If the fermion mass is larger than half the curvature of the compact dimension, the zero mode can be localized on the ``hidden'' 3-brane in the Randall-Sundrum model. Identifying this mode with a right-handed neutrino provides a new way for obtaining small Dirac neutrino masses without invoking a see-saw mechanism. Cancellation of the parity anomaly requires introducing an even number of bulk fermions. This naturally leads to a strong hierarchy of neutrino masses and generically large mixing angles.

hep-ph↗
arXiv1999

Trojan Penguins and Isospin Violation in Hadronic B Decays

Some rare hadronic decays of B mesons, such as B->pi K, are sensitive to isospin-violating contributions from physics beyond the Standard Model. Although commonly referred to as electroweak penguins, such contributions can often arise through tree-level exchanges of heavy particles, or through strong-interaction loop diagrams. The Wilson coefficients of the corresponding electroweak penguin operators are calculated in a large class of New Physics models, and in many cases are found not to be suppressed with respect to the QCD penguin coefficients. Several tests for these effects using observables in B->pi K decays are discussed, and nontrivial bounds on the couplings of the various New Physics models are derived.

hep-ph↗
arXiv1999

Neutrino propagation in matter with general interactions

We present a general analysis of the effective potential for neutrino propagation in matter, assuming a generic set of Lorentz invariant non-derivative interactions. We find that in addition to the known vector and axial vector terms, in a polarized medium also tensor interactions can play an important role. We compute the effective potential arising from a tensor interaction. We show that the components of the tensor potential transverse to the direction of the neutrino propagation can induce a neutrino spin-flip, similar to the one induced by a transverse magnetic field.

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