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Alakabha Datta

Publications and source records attributed to Alakabha Datta.

At least 109 records · Page 6Linked to original sources
arXiv2003

Nonleptonic $Λ_b$ decays to $D_s(2317)$, $D_s(2460)$ and other final states in Factorization

We consider nonleptonic Cabibbo--allowed $Λ_b$ decays in the factorization approximation. We calculate nonleptonic decays of the type $ Λ_b \to Λ_c P $ and $ Λ_b \to Λ_c V $ relative to $\bar{B}_d \to D^+ P$ and $\bar{B}_d \to D^+ V$ where we include among the pseudoscalar states(P) and the vector states(V) the newly discovered $D_s$ resonances, $D_s(2317)$ and $D_s(2460)$. In the ratio of $Λ_b$ decays to $D_s(2317)$ and $D_s(2460)$ relative to the $\bar{B}_d$ decays to these states, the poorly known decay constants of $D_s(2317)$ and $D_s(2460)$ cancel leading to predictions that can shed light on the nature of these new states. In general, we predict the $Λ_b$ decays to be larger than the corresponding $\bar{B}_d$ decays and in particular we find the branching ratio for $Λ_b \to Λ_c D_s(2460)$ can be between four to five times the branching ratio for $\bar{B}_d \to D^+ D_s(2460)$. This enhancement of $Λ_b$ branching ratios follows primarily from the fact that more partial waves contribute in $Λ_b$ decays than in $\bar{B}_d$ decays. Our predictions are largely independent of model calculations of hadronic inputs like form factors and decay constants.

hep-ph↗
arXiv2003

Extracting γfrom Bd(t) -> D(*)+ D(*)- and Bd -> Ds(*)+ D(*)- Decays

We show that the CP phase γcan be obtained from measurements of Bd(t) -> D(*)+ D(*)- and Bd -> Ds(*)+ D(*)-. These decays are related by flavor SU(3) in the limit where spectator-quark contributions are small. If the pseudoscalar-pseudoscalar decays Bd(t) -> D+ D- and Bd -> Ds+ D- are used, the leading-order SU(3)-breaking effect is f_Ds/f_D. The dependence on decay constants can be removed by using a double ratio involving two helicity states of the vector-vector decays Bd(t) -> D*+ D*- and Bd -> Ds*+ D*-. In this case the theoretical error arising from all sources is in the range 5-10%.

hep-ph↗
arXiv2003

Triple-Product Correlations in B -> V1 V2$ Decays and New Physics

In this paper we examine T-violating triple-product correlations (TP's) in B -> V1 V2 decays. TP's are excellent probes of physics beyond the standard model (SM) for two reasons: (i) within the SM, most TP's are expected to be tiny, and (ii) unlike direct CP asymmetries, TP's are not suppressed by the small strong phases which are expected in B decays. TP's are obtained via the angular analysis of B -> V1 V2. In a general analysis based on factorization, we demonstrate that the most promising decays for measuring TP's in the SM involve excited final-state vector mesons, and we provide estimates of such TP's. We find that there are only a handful of decays in which large TP's are possible, and the size of these TP's depends strongly on the size of nonfactorizable effects. We show that TP's which vanish in the SM can be very large in models with new physics. The measurement of a nonzero TP asymmetry in a decay where none is expected would specifically point to new physics involving large couplings to the right-handed b-quark.

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arXiv2003

Understanding the nature of $D_s(2317)$ and $D_s(2460)$ through nonleptonic B Decays

We consider the nonleptonic B decays $ B \to D^{(*)} D_s(2317)$ and $ B \to D^{(*)} D_s(2460)$, involving the newly discovered $D_s(2317)$ and the $D_s(2460)$ states. We find that experiments indicate disagreement with model calculations of their properties and/or breakdown of the factorization assumption for these decays . We point out that decays involving $B_s$ mesons where the $D_s$ resonances can be produced via the weak decay of the $b$ quark can provide further information about the nature of these newly discovered states. We also propose a model to calculate the two body nonleptonic decays $ B \to D^{(*)} D_s(2317)(D_s(2460))$, if the $D_s(2317)$ and $D_s(2460)$ are interpreted as $DK$ and $D^*K$ molecules.

hep-ph↗
arXiv2003

T violation in $B \to V V$ Decays in the SM and Beyond

In this talk, we describe T-violating triple-product correlations (TP's) in $B \to V_1 V_2$ decays. We point out that TP's in the SM are generally tiny. It is only in a few decays with excited vector mesons in the final state that measurable TP's may be obtained. On the other hand, TP's in models beyond the SM can be large, and hence TP correlations are excellent probes of new physics.

hep-ph↗
arXiv2003

A New State of Baryonium

The recent discovery of a narrow resonance in the decay $J/ψ\to γp \bar{p}$ is described as a zero baryon number, ``deuteron-like singlet ${}^1S_0 $'' state. The difference in binding energy of the deuteron (-2.225 MeV) and of the new state (-17.5 MeV) can be accounted for in a simple potential model with a $λ\cdot λ$ confining interaction.

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arXiv2002

New-Physics Effects on Triple-Product Correlations in Lambda_b Decays

We adopt an effective-lagrangian approach to compute the new-physics contributions to T-violating triple-product correlations in charmless Lambda_b decays. We use factorization and work to leading order in the heavy-quark expansion. We find that the standard-model (SM) predictions for such correlations can be significantly modified. For example, triple products which are expected to vanish in the SM can be enormous (~50%) in the presence of new physics. By measuring triple products in a variety of Lambda_b decays, one can diagnose which new-physics operators are or are not present. Our general results can be applied to any specific model of new physics by simply calculating which operators appear in that model.

hep-ph↗
arXiv2002

B_{d,s}^0 --> K^{(*)} K-bar^{(*)}: CP phase alpha and New Physics

The decays B_{d,s}^0 --> K^{(*)} K-bar^{(*)} can be used to measure the angle alpha of the CKM unitarity triangle. The theoretical error from SU(3) breaking is expected to be small, so that the determination of alpha is clean. Moreover, since B_{d,s}^0 --> K^{(*)} K-bar^{(*)} are pure penguin decays, they are particularly sensitive to the presence of new physics

hep-ph↗
arXiv2002

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.

hep-ph↗
arXiv2002

Non Standard $η-η^{\prime}$ mixing and the Nonleptonic B and $Λ_b$ Decays to $η$ and $η^{\prime}$

Radial mixing in the pseudoscalar $η-η^{\prime}$ systems can be generated from hyperfine interactions and annihilation terms. For the $η-η^{\prime}$ system we find the effects of radial mixing are appreciable and seriously affect the decay branching ratios for $B \to η(η^{\prime})K(K^*)$, mainly by modifying the $B \to η(η^{\prime})$ form factors. In particular, the effect of radial mixing in conjunction with the interference effects among penguin amplitudes can resolve puzzles in the $B \to η(η^{\prime}) K$ decays. The decay $Λ_b \to Λη(η^{\prime})$ on the other hand is dominated by a single amplitude so that the significant interference effects of B decays are absent here. Moreover, since no $Λ_b \to η(η^{\prime})$ form factors are involved here, the effect of radial mixing is essentially negligible. Hence, unlike the B system, we do not predict a large enhancement of $Λ_b \to Λη^{\prime}$ relative to $Λ_b \to Λη$.

hep-ph↗
arXiv2002

Measuring alpha using B -> K(*) Kbar(*) Decays

We describe a new method for obtaining the CP phase alpha via measurements of B_{d,s} -> K(*) Kbar(*) decays. This method is particularly appropriate for hadron colliders since some of the branching ratios are small [O(10^{-6})], and since B_s decays are involved. By comparing the value of alpha extracted from this method with that obtained in B -> pi pi or B -> rho pi decays, one can detect the presence of new physics in the b -> d penguin amplitude. The method does require theoretical input, but model calculations suggest that the theoretical uncertainty is at most 5%, and might well be even smaller. These estimates can be tested experimentally. The method is therefore quite clean.

hep-ph↗
arXiv2002

T-Violating Triple-Product Correlations in Charmless Lambda_b Decays

Using factorization, we compute, within the standard model, the T-violating triple-product correlations in the charmless decays Lambda_b -> F_1 F_2, where F_1 is a light spin-1/2 baryon and F_2 is a pseudoscalar (P) or vector (V) meson. We find a large triple-product asymmetry of 18% for the decay Lambda_b -> p K^-. However, for other classes of Lambda_b -> F_1 P decays, the asymmetry is found to be at most at the percent level. For Lambda_b -> F_1 V decays, we find that all triple-product asymmetries are small (at most O(1%)) for a transversely-polarized V, and are even smaller for longitudinal polarization. Our estimates of the nonfactorizable contributions to these decays show them to be negligible, and we describe ways of testing this.

hep-ph↗
arXiv2002

Difficulties in Obtaining Weak Phases from $b\to d$ Penguin Decays

We re-examine a recent proposal for obtaining βusing the measurements of the b -> d penguin decays B_d(t) -> K^0 \kbar and B_s(t) -> ϕK_S, along with a theoretical assumption. We show that there are in fact three assumptions one can make, so that the method can in principle be used to extract α, βor γ. We also show that it is the assumption which yields γwhich is the best. However, the theoretical error on this assumption is still 25-30%, which leads to an error on γof at least 20-25%. Given our current understanding of hadronic physics, it does not seem possible to reduce this error.

hep-ph↗
arXiv2002

Charmless B Decays to Final States with Radially Excited Vector Mesons

We consider the weak decays of a B meson to final states that contain a S-wave radially excited vector meson. We consider vector-pseudoscalar final states and calculate ratios of the type $B \to ρ^{\prime} π/B \to ρπ$, $B \to ω^{\prime} π/B \to ωπ$ and $B \to ϕ^{\prime} π/B \to ϕπ$ where $ρ^{\prime}$, $ω^{\prime}$ and $ϕ^{\prime}$ are higher $ρ$, $ω$ and $ϕ$ S-wave radial excitations. We find such decays to have larger or similar branching ratios compared to decays where the final state $ρ$, $ω$ and $ϕ$ are in the ground state. We also study the effect of radial mixing in the vector system generated from hyperfine interaction and the annihilation term.

hep-ph↗
arXiv2002

B -> K(*) Kbar(*) Decays: A New Method for Measuring the CP Phase α

We present a new method for measuring the CP phase α. It requires the measurement of the pure penguin decays Bd(t) -> K(*) Kbar(*) and B_s -> K(*) Kbar(*). The method is quite clean: we estimate the theoretical uncertainty to be at most 5%. By applying the method to several K(*) Kbar(*) final states, αcan be extracted with a fourfold ambiguity. An additional assumption reduces this ambiguity to twofold: {α, α+ π}. Since no \pi0 detection is needed, this method can be used at hadron colliders.

hep-ph↗
arXiv2001

Relations for two body B Decays to Charmonium and tests for $η-η^{\prime}$ mixing

The two body decays of $B_d$ and $B_s$ decays into $J/ψM$, where $M$ is a light meson, is studied under the very simple assumptions that the spectator quark does not play a role in the decay of the weak heavy quark or antiquark. This hypothesis leads to interesting relations between decay amplitudes. The assumption of SU(3) symmetry leads to additional relations between the decay amplitudes and in particular, the eight CP eigenstates $J/ψK_S$, $J/ψη$, $J/ψη^{\prime}$ and $J/ψπ^o$ are all given in terms of 0. If agreement with experiment validates these assumptions the parameters over determined by the results will give information about the ratio of penguin to tree contributions to the "golden channel" $B^o \to J/ψK_S$ decay and will provide tests for the standard $η-η^{\prime}$ mixing, which assumes that this mixing is determined by a single mixing angle, as well as determine the value of the mixing angle. We also present tests of the standard $η-η^{\prime}$ mixing involving semileptonic $D$ decays.

hep-ph↗
arXiv2001

Using Bs(t) -> phi K_s to measure Sin 2 beta

In this talk we show that, unlike other pure $b\to d$ penguin processes, the decay $\bs(t)\toϕ\ks$ is dominated by a single amplitude, that of the internal $t$-quark. Thus, the indirect CP asymmetry in this decay probes $\sin 2β$. This cancellation holds for most part of the parameter space and error on $\sin 2β$ is less than 10%. By measuring the direct CP asymmetry, one can get a better idea of the probable error on $\sin 2β$.

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