$B \to VV$ Decays - Polarization and Triple Products
We discuss how triple product asymmetries can be used to discover and constrain new physics in $B \to VV$ decays.
hep-ph↗
arXiv subjects
Alakabha Datta
Publications and source records attributed to Alakabha Datta.
New Physics in b -> s Transitions and the B_{d,s}^0 -> V_1 V_2 Angular Analysis
We suppose that there is new physics (NP) in b -> s transitions, and examine its effect on the angular distribution of B_q^0 -> V_1 V_2 (q=d,s), where V_{1,2} are vector mesons. We find that, in the presence of such NP, the formulae relating the parameters of the untagged, time-integrated angular distribution to certain observables (polarization fractions, CP-violating triple-product asymmetries, CP-conserving interference term) must be modified from their standard-model forms. This modification is due in part to a nonzero B^0_q-Bbar^0_q width difference, which is significant only for B^0_s decays. We re-analyze the B^0_s -> phi phi data to see the effect of these modifications. As (Delta Gamma_s/2)/Gamma_s ~ 10%, there are O(10%) changes in the derived observables. These are not large, but may be important given that one is looking for signals of NP. In addition, if the NP contributes to the b -> s decay, the measurement of the untagged time-dependent angular distribution provides enough information to extract all the NP parameters.
hep-ph↗
Measuring beta_s with Bs -> K0(*) K0bar(*) -- a Reappraisal
The Bs-Bsbar mixing phase, beta_s, can be extracted from Bs -> K0(*) K0bar(*), but there is a theoretical error if the second amplitude, Vub* Vus P'uc, is non-negligible. Ciuchini, Pierini and Silvestrini (CPS) have suggested measuring Puc in Bd -> K0(*) K0bar(*), and relating it to P'uc using SU(3). For their choice of the direct and indirect CP asymmetries in Bd -> K0(*) K0bar(*), they find that the error on beta_s is very small, even allowing for 100% SU(3) breaking. In this paper, we re-examine the CPS method, allowing for a large range of the Bd -> K0(*) K0bar(*) observables. We find that the theoretical error in the extraction of beta_s can be quite large, up to 18 degrees. This problem can be ameliorated if the value of SU(3) breaking were known, and we discuss different ways, both experimental and theoretical, of determining this quantity.
hep-ph↗
The charged lepton mass matrix and non-zero $θ_{13}$ with TeV scale New Physics
We provide an explicit structure of the charged lepton mass matrix which is 2-3 symmetric except for a single breaking of this symmetry by the muon mass. We identify a flavor symmetric limit for the mass matrices where the first generation is decoupled from the other two in the charged lepton sector while in the neutrino sector the third generation is decoupled from the first two generations. The leptonic mixing in the symmetric limit can be, among other structures, the bi-maximal (BM) or the tri-bimaximal (TBM) mixing. Symmetry breaking effects are included both in the charged lepton and the neutrino sector to produce corrections to the leptonic mixing and explain the recent $θ_{13}$ measurements. A model that extends the SM by three right handed neutrinos, an extra Higgs doublet, and two singlet scalars is introduced to generate the leptonic mixing.
hep-ph↗
New Physics in b -> s mu+ mu-: CP-Violating Observables
We perform a comprehensive study of the impact of new-physics operators with different Lorentz structures on CP-violating observables involving the b -> s mu+ mu- transition. We examine the effects of new vector-axial vector (VA), scalar-pseudoscalar (SP) and tensor (T) interactions on the CP asymmetries in the branching ratios and forward-backward asymmetries of Bs -> mu mu, B -> Xs mu mu, Bs -> mu mu gamma, B -> K mu mu, and B -> K* mu mu. In B -> K* mu mu, we also explore the direct CP asymmetries in the longitudinal polarization fraction f_L and the angular asymmetries A_T^{(2)} and A_{LT}, as well as the triple-product CP asymmetries A_T^{(im)} and A^{(im)}_{LT}. We find that, in almost all cases, the CP-violating observables are sensitive only to new physics which involves VA operators. The VA new physics may therefore be unambiguously identified by a combined analysis of future measurements of these CP-violating observables.
hep-ph↗
The Top Forward Backward Asymmetry with general Z ' couplings
The measurement of the top forward-backward asymmetry in $\ttbar$ production measured at the Tevatron shows deviation from the Standard Model prediction. A $ u \to t$ transition via a flavor changing $Z^{\prime}$ can explain the data. We show that left handed $t_Lu_LZ^{\prime}$ couplings can be constrained from $B_{d,s}$ mixing while the constrains on the right handed couplings $t_R u_R Z^{\prime}$ vanish in the limit of $m_u \to 0$. We then consider the most general form of the $t uZ^{\prime}$ interaction which includes vector-axial vector as well as tensor type couplings and study how these couplings affect the top forward-backward asymmetry.
hep-ph↗
Study of CP violation in $Λ_c^+$ decay
In this paper, we study CP violation in $Λ_c^+\to BP$ and $Λ_c^+\to BV$ decays, where $B,P$ and $V$ denote a light spin-1/2 baryon, pseudoscalar and a vector meson respectively. In these processes the $T$ odd CP violating triple-product (TP) correlations are examined. The genuine CP violating observables which are composed of the helicity amplitudes occurring in the angular distribution are constructed. Experimentally, by performing a full angular analysis it is shown how one may extract the helicity amplitudes and then obtain the TP asymmetries. We estimate the TP asymmetries in $\lam$ decays to be negligible in the standard model making these processes an excellent place to look for new physics. Taking a two Higgs doublet model, as an example of new physics, we show that large TP asymmetries are possible in these decays. Finally, we discuss how BES-III and Super $τ$-Charm experiments will be sensitive to these CP violating signals in $Λ_c^+$ decays.
hep-ph↗
Like-sign dimuon charge asymmetry in Randall-Sundurm model
We confirm that in order to account for the recent DØ result of large like-sign dimuon charge asymmetry, a considerable large new physics effect in $Γ_{12}^s$ is required in addition to a large CP violating phase in $B_s -\bar{B}_s$ mixing. In the Randall-Sundrum model of warped geometry, where the fermion fields reside in the bulk, new sources of flavor and CP violation are obtained. We analyze the like-sign dimuon asymmetry in this class of model, as an example of the desired new physics. We show that the wrong charge asymmetry, $a_{sl}^s$, which is related to the dimuon asymmetry, is significantly altered compared to the Standard Model value. However, experimental limits from $ΔM_s$, $ΔΓ_s$ as well as $K$ mixing and electroweak corrections constrain it to be greater than a $σ$ away from its experimental average value. This model cannot fully account for the DØ anomaly due to its inability to generate sufficient new contribution to the width difference $Γ^s_{12}$, even though the model can generate large contribution to the mass difference $M^s_{12}$.
hep-ph↗
Searching for New Physics with B-Decay Fake Triple Products
In pure-penguin bbar -> sbar B -> V_1 V_2 decays (V_{1,2} are vector mesons), fT/fL ~= 1 has been observed (fT (fL) 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 paper, we show that these two explanations can be partially distinguished through the triple products (TP's) in these transitions. In particular, the SM predicts one of the two fake, CP-conserving TP's 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 TP's in B -> phi K* -- the present data prefer a SM explanation of fT/fL -- and provide the SM predictions for Bs -> phi phi.
hep-ph↗
Probing light pseudoscalar, axial vector states through $η_{b} \toτ^{+}τ^{-}$
In this paper we explore the decay $η_b --> τ^+ τ^-$ as a probe for a light pseudoscalar or a light axial vector state. We estimate the standard model branching ratio for this decay to be $~4\times 10^{-9}$. We show that considerably larger branching ratios, up to the present experimental limit of ~8%, is possible in models with a light pseudoscalar or a light axial vector state. As we do not include possible mixing effects between the light pseudoscalar and the $η_b$, our results should be reliable when the pseudoscalar mass is away from the $η_b$ mass.
hep-ph↗
New Physics in Bs -> J/psi phi: a General Analysis
Recently, the CDF and D0 collaborations measured indirect CP violation in Bs -> J/psi phi and found a hint of a signal. If taken at face value, this can be interpreted as a nonzero phase of Bs-Bsbar mixing (beta_s), in disagreement with the standard model, which predicts that beta_s ~= 0. In this paper, we argue that this analysis may be incomplete. In particular, there can be new physics (NP) in the bbar -> sbar c cbar decay. If so, the value of beta_s is different than for the case in which NP is assumed to be present only in the mixing. We have examined several models of NP and found that, indeed, there can be significant contributions to the decay. These effects are consistent with measurements in B -> J/psi K* and Bd -> J/psi Ks. Due to the NP in the decay, polarization-dependent indirect CP asymmetries and triple-product asymmetries are predicted in Bs -> J/psi phi.
hep-ph↗
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 -> cV where V = γ, Z. We find branching fractions for these decays within possible reach of the LHC. Predictions are also made for t -> sW.
hep-ph↗
Supersymmetry and CP violation in B^0_s - \bar{B}^0_s mixing and B^0_s -> J/ψϕdecay
Supersymmetric contributions to time independent asymmetry in $B^0_s \to J/ψϕ$ process are analyzed in the view of the recent Tevatron experimental measurements. We show that the experimental limits of the mass difference $ΔM_{B_s}$ and the mercury EDM significantly constrain the SUSY contribution to $B^0_s -\bar{B}^0_s$ mixing, so that $\sin 2 β_s \lsim 0.1$. We also point out that the one loop SUSY contribution to $B^0_s \to J/ψϕ$ decay can be important and can lead to large indirect CP asymmetries which are different for different polarization states. These new physics effects in the decay amplitude can be consistent with CP measurements in the $B_d$ system.
hep-ph↗
B -> phi K*, B -> phi Ks and New Physics
We consider the new-physics (NP) solution to the polarization puzzle in B -> phi K* decays. We note that any such solution must reproduce the data in B -> phi Ks, where there are disagreements with the standard model in CP-asymmetry measurements. We examine 10 NP operators, of S/P, V/A and T variety. We find that, as long as B -> phi Ks exhibits large CP-violating effects, no single operator can explain the observations in both B -> phi K* and B -> phi Ks. For 2-NP-operator solutions, there are four possibilities, all of S/P type, which are presently allowed. We discuss ways of distinguishing among these solutions in the future. Models which contain only V/A operators, such as those with supersymmetry or extra Z' bosons, cannot explain both B -> phi Ks and B -> phi K* data. On the other hand, the two-Higgs-doublet model, which has only S/P operators, is favored.}
hep-ph↗
Final-state Polarization in Bs Decays
Certain Bs --> V_1V_2 decays (V_i is a vector meson) can be related by flavor SU(3) symmetry to corresponding Bd --> V_3V_4 decays. In this paper, we show that the final-state polarization can be predicted in the Bs decay, assuming polarization measurements of the Bd decay. This can be done within the scenario of penguin annihilation (PA), which has been suggested as an explanation of the unexpectedly large transverse polarization in B-->phi K^*. PA is used to estimate the breaking of flavor SU(3) symmetry in pairs of decays. Two of these for which PA makes a reasonably precise prediction of the size of SU(3) breaking are (Bs --> phiphi, Bd --> phi K^{0*}) and (Bs --> phi {\bar K}^{0*}, Bd --> {\bar K}^{0*} K^{0*}). The polarization measurement in the Bd decay can be used to predict the transverse polarization in the Bs decay, and will allow a testing of PA.
hep-ph↗
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 $\sin{θ_{13}}$ to be related to the deviation $\sin{θ_{12}}$ from $\sqrt{1/3}$ while the deviation of $\sin{θ_{23}}$ from its tri-bimaximal value is $ \sim {m_μ \over m_τ}$.
hep-ph↗
CP violation in tau -> K pi pi nu_tau
We consider CP-violating effects in tau->K pi pi nu_tau, assuming that a charged Higgs boson provides a new amplitude that can interfere with the usual Standard Model amplitude. We consider four CP-odd observables -- the regular rate asymmetry, two modified rate asymmetries and a triple-product asymmetry. The regular rate asymmetry is expected to be small because it requires the interference of the new physics amplitude with the standard model amplitude containing the hadronic scalar form factor. The other CP asymmetries may be more promising in terms of their new physics reach. Numerical estimates indicate that the maximum obtainable values for the modified and triple-product asymmetries are on the order of a percent.
hep-ph↗
Suppressed FCNC in New Physics with Shared Flavor Symmetry
Many extensions of the Standard Model(SM) generate contributions to Flavor Changing Neutral Current(FCNC) processes that must have sufficient flavor suppression to be consistent with experiments, if the new physics (NP) is associated with a scale of a TeV. Here we present a mechanism for suppressing the NP effects to FCNC processes. We consider the possibility that the source of NP contributions to FCNC processes share the same flavor symmetry underlying the SM source of FCNC processes which are the quark and lepton mass matrices. We call this the principle of shared flavor symmetry. In the flavor symmetric limit, the quark and lepton mixing matrices have fixed forms and there are no NP FCNC processes. In the flavor symmetric limit, we take the quark mixing matrix to be the identity matrix and the lepton mixing matrix to be given by tri-bimaximal mixing. Realistic mixing matrices are obtained by the small breaking of the flavor symmetry. New contributions to FCNC processes arise because of non universal breaking of the flavor symmetry in the quark and lepton mass matrices and the NP sources of FCNC processes. In particular, we will focus on new FCNC effects that arise due to the breaking of flavor symmetry only in the quark and charged lepton mass matrices but not in the NP sector. In this scenario, NP contributions to FCNC processes is linked to the source of flavor symmetry breaking in the quark and charged lepton mass matrices. To demonstrate the mechanism we use a two higgs doublet model as an example of beyond the SM physics though one should be able to adapt this mechanism to other models of new physics.
hep-ph↗