arXiv subjects

Maxime Imbeault

Publications and source records attributed to Maxime Imbeault.

At least 19 recordsLinked to original sources

arXiv2023

Charmless $B\to PPP$ Decays: the Fully-Antisymmetric Final State

Under flavor $SU(3)$ symmetry (SU(3)$_F$), the final-state particles in $B\to PPP$ decays ($P$ is a pseudoscalar meson) are treated as identical, and the $PPP$ must be in a fully-symmetric (FS) state, a fully-antisymmetric (FA) state, or in one of four mixed states. In this paper, we present the formalism for the FA states. We write the amplitudes for the 22 $B\to PPP$ decays that can be in an FA state in terms of both SU(3)$_F$ reduced matrix elements and diagrams. This shows the equivalence of diagrams and SU(3)$_F$. We also give 15 relations among the amplitudes in the SU(3)$_F$ limit, as well as the additional four that appear when the diagrams $E$/$A$/$PA$ are neglected. We present sets of $B \to PPP$ decays that can be used to extract $\gamma$ using the FA amplitudes. The value(s) of $\gamma$ found in this way can be compared with the value(s) found using the FS states.

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arXiv2014

Charmless B -> PPP Decays: the Fully-Symmetric Final State

In charmless B -> PPP decays, where P is a pseudoscalar meson, there are six possibilities for the symmetry of the final state. In this paper, for P=pi,K, we examine the properties of the fully-symmetric final state. We present expressions for all 32 B -> PPP decay amplitudes as a function of both SU(3) reduced matrix elements and diagrams, demonstrating the equivalence of diagrams and SU(3). We also give 25 relations among the amplitudes in the SU(3) limit, as well as those that appear when the diagrams E/A/PA are neglected. In the SU(3) limit, one has the equalities \sqrt{2} A(B+ -> K+ pi+ pi-)_{FS} = A(B+ -> K+ K+ K-)_{FS} and \sqrt{2} A(B+ -> pi+ K+ K-)_{FS} = A(B+ -> pi+ pi+ pi-)_{FS}, where FS denotes the fully-symmetric final state. These provide good tests of the standard model that can be carried out now by the LHCb Collaboration.

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arXiv2013

Extraction of the CP-violating phase $γ$ using $B \to K ππ$ and $B \to K K {\bar K}$ decays

Using the B{\sc a}B{\sc ar}\ measurements of the Dalitz plots for $B^0 \to K^+π^0π^-$, $B^0 \to K^0π^+π^-$, $B^+ \to K^+π^+π^-$, $B^0 \to K^+ K^0 K^-$, and $B^0 \to K^0 K^0 {\bar K}^0$ decays, we demonstrate that it is possible to cleanly extract the weak phase $γ$. We find four possible solutions. Three of these -- $32^\circ$, $259^\circ$, and $315^\circ$ -- are in disagreement with the SM, while one -- $77^\circ$ -- is consistent with the SM. An advantage of this Dalitz-plot method is that one can obtain many independent measurements of $γ$, thereby reducing its statistical error. An accurate determination of the errors, however, requires detailed knowledge of the data.

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arXiv2013

Measurement of $γ$ from three-body B decays

Using the BaBar measurements of the Dalitz plots for the decays $B^0 \to K^+π^0π^-$, $B^0 \to K^0π^+π^-$, $B^+ \to K^+π^+π^-$, $B^0 \to K^+ K^0 K^-$, and $B^0 \to K^0 K^0 \bar K^0$, we demonstrate that it is possible to cleanly extract the weak phase $γ$. An advantage of this Dalitz-plot method is that one can obtain many independent measurements of $γ$, thereby reducing its statistical error. An accurate determination of the errors, however, requires detailed knowledge of the data. Hopefully, an experimental group will repeat the analysis, and obtain precise values of the errors.

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arXiv2013

Measurement of gamma using B -> K pi pi and B -> K K Kbar decays

The BaBar measurements of the Dalitz plots for B0 -> K+ pi0 pi-, B0 -> K0 pi+ pi-, B+ -> K+ pi+ pi-, B0 -> K+ K0 K-, and B0 -> K0 K0 Kbar0 decays are used to cleanly extract the weak phase gamma. We find four possible solutions: $(31^{+2}_{-3})^\circ$, $(77 \pm 3)^\circ$, $(258^{+4}_{-3})^\circ$, and $(315^{+3}_{-2})^\circ$. One solution -- $(77 \pm 3)^\circ$ -- is consistent with the SM. Its error, which includes leading-order flavor-SU(3) breaking, is far smaller than that obtained using two-body B decays.

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arXiv2012

Extraction of $γ$ from three-body B decays

The conventional use of two-body B decays to extract $γ$, although theoretically clean, is currently statistics-limited. On the other hand, a bulk of data on three-body B decays is available from $B$ factories. Applying the flavor-SU(3)-symmetric approach proposed in Ref.\ \cite{ReyLeLorier:2011ww} to \babar data, we find the highly promising result $γ= (81^{+4}_{-5} ({\rm avg.}) \pm 5 ({\rm std.\ dev.}))^\circ$. This establishes the use of three-body B decays as a viable alternative for the extraction of weak phases. In this preliminary analysis we have neglected several sources of uncertainties such as the effect of flavor-SU(3) breaking due to meson masses, and error correlations between input experimental parameters. A better understanding of these will improve the viability of this method.

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arXiv2012

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.

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arXiv2011

SU(3) Breaking in Charmless B Decays

There are many charmless B decay pairs whose amplitudes are related by U spin (d <--> s) or flavor SU(3). The theoretical uncertainty in any analysis involving such pairs must take into account U-spin/SU(3) breaking. In the past, such considerations generally used theoretical input, but we show that this can be experimentally measured. We present lists of two- and three-body decay pairs from which the size of the breaking can be obtained. We detail the values of U-spin/SU(3) breaking given by the present experimental data. One pair -- Bd -> pi+ pi- and Bd -> pi- K+ -- exhibits large nonfactorizable breaking. We present other signals of SU(3) breaking in two- and three-body decays, and discuss further tests for nonfactorizable effects. Finally, we also point out that the pure-penguin decay Bs -> Kbar0 Kbar0 K0 is intriguing because it can be used to cleanly probe the Bs-Bsbar mixing phase.

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arXiv2011

Diagrammatic Analysis of Charmless Three-Body B Decays

We express the amplitudes for charmless three-body B decays in terms of diagrams. In addition, we show how to use Dalitz-plot analyses to obtain decay amplitudes which are symmetric or antisymmetric under the exchange of two of the final-state particles. When annihilation-type diagrams are neglected, as in two-body decays, many of the exact, purely isospin-based results are modified, leading to new tests of the standard model (SM). Some of the tests can be performed now, and we find that present data agree with the predictions of the SM. Furthermore, contrary to what was thought previously, it is possible to cleanly extract weak-phase information from three-body decays, and we discuss methods for B -> K pi pi, K K Kbar, K Kbar pi and pi pi pi.

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arXiv2011

Measuring gamma in B -> K pi pi Decays

We re-examine the question of measuring the weak phase gamma in B -> K pi pi decays. To this end, we express all B -> K pi pi amplitudes in terms of diagrams. We show that, as in B -> K pi, there exist relations between certain tree and electroweak-penguin diagrams. The imposition of these relations allows the extraction of gamma from measurements of the B -> K pi pi observables. We estimate the theoretical error in this method to be O(5%).

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arXiv2008

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.}

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arXiv2008

The B-->pi K Puzzle and Supersymmetry

At present, there are discrepancies between the measurements of several observables in B-->pi K decays and the predictions of the standard model (the ``B-->pi K puzzle''). Although the effect is not yet statistically significant -- it is at the level of $\gsim 3σ$ -- it does hint at the presence of new physics. In this paper, we explore whether supersymmetry (SUSY) can explain the B-->pi K puzzle. In particular, we consider the SUSY model of Grossman, Neubert and Kagan (GNK). We find that it is extremely unlikely that GNK explains the B-->pi K data. We also find a similar conclusion in many other models of SUSY. And there are serious criticisms of the two SUSY models that do reproduce the B-->pi K data. If the B-->pi K puzzle remains, it could pose a problem for SUSY models.

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arXiv2007

Extracting alpha from B0(d) --> K0 anti-K0 Decays

We propose a new method for obtaining the CP phase alpha, based on measurements of B0(d) --> K0 anti-K0, along with theoretical input. Due to the similarities of QCD factorization (QCDf) and perturbative QCD (pQCD), this input is basically the same for each of these models. Although the theoretical error is large at present, many of the contributing quantities will be better known in the future, leading to a smaller error. One outstanding question is the extent to which the precision on quark masses, especially m_c/m_b, can be improved. If one assumes that new physics is not present, the method can be used to predict the values of CP asymmetries in B0(d) --> K0 anti-K0: 0.02 <= A_{dir}^2 + A_{mix}^2 <= 0.125. A result outside this range would signal the existence of long-distance effects beyond those included in models of nonleptonic decays based on factorization (such as QCDf and pQCD), or the presence of new physics.

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arXiv2006

Patterns of New Physics in B Decays

We show that any new physics (NP) which affects B decays with penguin contributions can be absorbed by redefinitions of the standard-model (SM) diagrammatic amplitudes. Hence, there are no clean signals of NP in such decays unless there is an accurate theoretical estimate of parameters or a justifiable approximation can be made. In all decays with penguin contributions, NP simultaneously affects pairs of diagrams. The evidence for a large C' from fits to B-> pi K data is naturally explained if NP contributes to P_EW, since NP affects the P_EW and C' diagrams as a pair. The weak phase gamma measured in B-> pi K decays will always agree with its SM value even in the presence of NP, if the NP contributes in such a way that the amplitudes retain the SM form after suitable redefinitions.

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arXiv2006

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 rigourous. 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 alpha_s, 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 re-evaluate the question of whether there is a ``B -> pi K puzzle.'' At O(alpha_s^0), we find that the diagram ratio |C'/T| is about 0.17, a factor of 10 too small to explain all the B -> pi K data. Both QCDfac and pQCD find that, at O(α_s^1), 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 O(α_s^0) result, and that there really is a B -> pi K puzzle.

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arXiv2005

Relative Sizes of Diagrams in B -> pi pi, pi K Decays

We show that the neglect of the $(V-A)\times (V+A)$ pieces of the electroweak penguin (EWP) amplitudes in the effective hamiltonian (the Wilson coefficients are very small) allows one to calculate the relative size of some tree and EWP diagrams in $B \to ππ$ and $B\to πK$ decays. For both decay classes, tree and EWP amplitudes are related using only isospin. In $B\to ππ$, the ratio $C/T$ is calculated using isospin alone; in $B\to πK$ it is found using flavor SU(3) symmetry. These results are obtained by computing explicitly all Wick contractions of all effective operators. Relations among these contractions are found using Fierz identities and final-state symmetry arguments.

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arXiv2005

Methods for Measuring New-Physics Parameters in B Decays

Recently, it was argued that new-physics (NP) effects in B decays can be approximately parametrized in terms of a few quantities. As a result, CP violation in the $B$ system allows one not only to detect the presence of new physics (NP), but also to measure its parameters. This will allow a partial identification of the NP, before its production at high-energy colliders. In this paper, we examine three methods for measuring NP parameters. The first uses a technique involving both $\btos$ and $\btod$ penguin B decays. Depending on which pair of decays is used, the theoretical error is in the range 5--15%. The second involves a comparison of $B\to πK$ and $B\toππ$ decays. Although the theoretical error is large ($\gsim 25%$), the method can be performed now, with presently-available data. The third is via a time-dependent angular analysis of $\bvv$ decays. In this case, there is no theoretical error, but the technique is experimentally challenging, and the method applies only to those NP models whose weak phase is universal to all NP operators. A reliable identification of the NP will involve the measurement of the NP parameters in many different ways, and with as many B decay modes as possible, so that it will be important to use all of these methods.

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arXiv2004

CP Violation in B -> pi K Decays

I briefly review CP violation in the B system, concentrating on B -> pi K decays. I discuss how to deal with electroweak-penguin contributions to these decays using flavour SU(3). With these, I show that the entire unitarity triangle can be extracted from measurements of B -> pi K decays. Finally, I examine the signals for new physics in these decays and the possibilities for measuring them.

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