arXiv subjects

Patricia Ball

Publications and source records attributed to Patricia Ball.

At least 19 recordsLinked to original sources

arXiv2011

Symmetries and Asymmetries of B -> K* mu+ mu- Decays in the Standard Model and Beyond

The rare decay B -> K* (-> K pi) mu+ mu- is regarded as one of the crucial channels for B physics as the polarization of the K* allows a precise angular reconstruction resulting in many observables that offer new important tests of the Standard Model and its extensions. These angular observables can be expressed in terms of CP-conserving and CP-violating quantities which we study in terms of the full form factors calculated from QCD sum rules on the light-cone, including QCD factorization corrections. We investigate all observables in the context of the Standard Model and various New Physics models, in particular the Littlest Higgs model with T-parity and various MSSM scenarios, identifying those observables with small to moderate dependence on hadronic quantities and large impact of New Physics. One important result of our studies is that new CP-violating phases will produce clean signals in CP-violating asymmetries. We also identify a number of correlations between various observables which will allow a clear distinction between different New Physics scenarios.

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arXiv2009

Constraining New Physics in B-->pi+pi- with Reparametrization Invariance and QCD Factorization

Usually, B->pi+pi- decays are expressed in terms of weak amplitudes explicitly dependent on the CKM weak phase alpha or gamma. In this letter, we show that the weak amplitudes can be rewritten such that a manifest dependence on beta emerges instead. Based on this, we constrain new-physics contributions to the CP-violating phase phi_d in B_0 anti-B_0 mixing. Further, we apply reparametrization invariance and use QCD factorization predictions to investigate the bounds on an additional new-physics amplitude in B->pi+pi-.

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arXiv2008

Distribution Amplitudes of the Lambda_b Baryon in QCD

The QCD description of exclusive decays of the $Λ_b$ baryon involves hadronic matrix elements of non-local light ray operators, the light-cone distribution amplitudes. We introduce the complete set of three--quark distribution amplitudes and calculate the renormalization scale dependence for the leading twist. At leading order in the strong coupling the evolution is driven by pairwise two--quark interactions: heavy--light involving Sudakov logarithms as in the B-meson case, and light--light as in light mesons. We solve the evolution equation and show that its main effect is to generate a radiative tail extending to high energies. Finally, we present simple models for the distribution amplitudes based on QCD sum rules, and study the effect of the evolution on these models.

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arXiv2007

B->eta(') Form Factors in QCD

We calculate the semileptonic form factors $f_+^{B\to η}(q^2)$ and $f_+^{B\to η'}(q^2)$ from QCD sum rules on the light-cone (LCSRs), to NLO in QCD, and for small to moderate q^2, $0\leq q^2\leq 16 {\rm GeV}^2$. We include in particular the so-called singlet contribution, i.e.\ weak annihilation of the B meson with the emission of two gluons which, thanks to the U(1)$_{\rm A}$ anomaly, couple directly to $\etap$. This effect is included to leading-twist accuracy. This contribution has been neglected in previous calculations of the form factors from LCSRs. We find that the singlet contribution to $f_+^{B\to η'}$ can be up to 20%, while that to $f_+^{B\to η}$ is, as expected, much smaller and below 3%. We also suggest to measure the ratio ${\cal B}(B\toη' e ν)/{\cal B}(B\to ηe ν)$ to better constrain the size of the singlet contribution.

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arXiv2007

Twist-4 Distribution Amplitudes of the K$^*$ and $ϕ$ Mesons in QCD

We present a systematic study of twist-4 light-cone distribution amplitudes of the $K^*$ and $ϕ$ meson in QCD. The structure of SU(3)-breaking corrections is studied in detail. Non-perturbative input parameters are estimated from QCD sum rules and a renormalon based model. As a by-product, we give a complete reanalysis of the parameters of the twist-4 $ρ$-meson distribution amplitudes.

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arXiv2007

|V_{ub}| from the Spectrum of B->pi e nu

I discuss the results for $|V_{ub}|f_+(0)$ and $|V_{ub}|$ obtained from the spectrum of $B\toπe ν$ and the form factor $f_+(q^2)$ from QCD sum rules on the light-cone and unquenched lattice calculations; the shape of $f_+(q^2)$ is fixed from experimental data.

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arXiv2007

Implication of the D^0 Width Difference On CP-Violation in D^0-\bar D^0 Mixing

Both BaBar and Belle have found evidence for a non-zero width difference in the $D^0$-$\bar D^0$ system. Although there is no direct experimental evidence for CP-violation in $D$ mixing (yet), we show that the measured values of the width difference $y\sim ΔΓ$ already imply constraints on the CP-violating phase in $D$ mixing, which, if significantly different from zero, would be an unambiguous signal of new physics.

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arXiv2007

Basics of D0-\bar D0 Mixing

Complementing the presentations, at this conference, of the first experimental evidence for $D$ mixing found at BaBar and Belle, I discuss the theoretical status of $D$ mixing.

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arXiv2007

Probing New Physics Through Bs Mixing

I discuss the interpretation of the recent experimental data on $B_s$ mixing in terms of model-independent new-physics parameters.

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arXiv2007

Twist-3 Distribution Amplitudes of K* and phi Mesons

We present a systematic study of twist-3 light-cone distribution amplitudes of $K^*$ and $ϕ$ mesons in QCD. The structure of SU(3)-breaking corrections is studied in detail. Non-perturbative input parameters are estimated from QCD sum rules. As a by-product, we update the parameters describing the twist-3 distribution amplitudes of the $ρ$ meson. We also review and update predictions for the twist-2 distribution amplitudes of $ρ$, $K^*$ and $ϕ$.

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arXiv2007

B->V gamma Beyond QCD Factorisation

We calculate the main observables in $B_{u,d}\to (ρ,ω,K^*)γ$ and $B_s\to (\bar K^*,ϕ)γ$ decays, i.e. branching ratios and CP and isospin asymmetries. We include QCD factorisation results and also the dominant contributions beyond QCD factorisation, namely long-distance photon emission and soft-gluon emission from quark loops. All contributions beyond QCD factorisation are estimated from light-cone sum rules. We devise in particular a method for calculating soft-gluon emission, building on earlier ideas developed for analogous contributions in non-leptonic decays. Our results are relevant for new-physics searches at the $B$ factories, the LHC and a future super-flavour factory. Using current experimental data, we also extract $|V_{td}/V_{ts}|$ and the angle $γ$ of the unitarity triangle. We give detailed tables of theoretical uncertainties of the relevant quantities which facilitates future determinations of these CKM parameters from updated experimental results.

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arXiv2007

Constraints on New Physics from gamma and |V_ub|

The SM unitarity triangle (UT) is completely determined by the parameters $γ$ and $|V_{ub}|$ which can be extracted from tree-level processes and are assumed to be free of new physics. By comparison with other determinations of UT parameters one can impose constraints on new physics in loop processes, in particular $B$ mixing.

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arXiv2006

|V_td/V_ts| from QCD Sum Rules on the Light-Cone

The dominant theoretical uncertainty in extracting $|V_{td}/V_{ts}|$ from the ratio of branching ratios $R_{ρ/ω}\equiv\bar{\cal B}(B\to (ρ,ω)γ)/\bar{\cal B}(B\to K^* γ)$ is given by the ratio of form factors $ξ_ρ\equiv T_1^{B\to K^*}(0)/T_1^{B\to ρ}(0)$. We find $ξ_ρ= 1.17\pm 0.09$ from QCD sum rules on the light-cone. Using QCD factorisation for the branching ratios, including the most dominant power-suppressed effects beyond QCD factorisation, and the current experimental results for $R_{ρ/ω}$, this translates into $|V_{td}/V_{ts}|_{\rm BaBar} = 0.199^{+0.023}_{-0.025}({\rm exp})\pm 0.014 ({\rm th})$, which corresponds to $γ_{\rm BaBar} = (61.0^{+13.5}_{-16.0}({\rm th}){}^{+8.9}_{-9.3}({\rm th}))$, and $|V_{td}/V_{ts}|_{\rm Belle} = 0.207^{+0.028}_{-0.033}({\rm exp}) ^{+0.014}_{-0.015}({\rm th})$, $γ_{\rm Belle} = (65.7^{+17.3}_{-20.7}({\rm exp})^{+8.9}_{-9.2}({\rm th}))^\circ$.

hep-ph↗

arXiv2006

|V_{ub}| from B-> pi e nu

I discuss the results for $|V_{ub}|$ obtained from $B\toπe ν$ using the form factor $f_+(q^2)$ from QCD sum rules on the light-cone and unquenched lattice calculations; the shape of $f_+(q^2)$ is fixed from experimental data.

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arXiv2006

|V_ub| from UTangles and B->pi l nu

The angles of the CKM unitarity triangle are now known well enough to allow a determination of its sides from global fits, with good accuracy. Assuming that new physics does not affect the angles, UTfit and CKMfitter find $|V_{ub}| = (3.50\pm 0.18)\times 10^{-3}$. Using this result, and new high-precision data on the spectrum of $B\toπ\ellν$ decays from BaBar, we find $|V_{ub}| f_+(0) = (9.1\pm 0.7)\times 10^{-4}$ and $f_+(0) = 0.26\pm 0.02$, with $f_+$ the $B\toπ$ weak transition form factor. These results are {\em completely model-independent}. We compare them to theoretical calculations from lattice and QCD sum rules on the light-cone.

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arXiv2006

Time-dependent CP Asymmetry in B->K* gamma as a (Quasi) Null Test of the Standard Model

We calculate the dominant Standard Model contributions to the time-dependent CP asymmetry in B0->K*0 gamma, which is O(1/mb) in QCD factorisation. We find that, including all relevant hadronic effects, in particular from soft gluons, the asymmetry S is very small, S=-0.022\pm 0.015^{+0}_{-0.01}, and smaller than suggested recently from dimensional arguments in a 1/mb expansion. Our result implies that any significant deviation of the asymmetry from zero, and in particular a confirmation of the current experimental central value, S_{HFAG}=-0.28\pm 0.26, would constitute a clean signal for new physics.

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arXiv2006

|V_td/V_ts| from B-> V gamma

The dominant theoretical uncertainty in extracting |V_td/V_ts| from the ratio of branching ratios R=B(B->(rho,omega)gamma)/B(B->K* gamma) is given by the ratio of form factors xi=T_1^{B->K*}(0)/T_1^{B->rho}(0). We re-examine xi in the framework of QCD sum rules on the light-cone, taking into account hitherto neglected SU(3)-breaking effects. We find xi=1.17 \pm 0.09. Using QCD factorisation for the branching ratios, and the current experimental average for R quoted by HFAG, this translates into |V_td/V_ts|^HFAG_{B->V gamma} = 0.192 \pm 0.014(th) \pm 0.016(exp). This result agrees, within errors, with that obtained from the Standard Model unitarity triangle, |V_td/V_ts|_SM = 0.216 \pm 0.029, based on tree-level-only processes, and with |V_td/V_ts|_{Delta m} = 0.2060^{+0.0081}_{-0.0060}(th) \pm 0.0007(exp), from the CDF measurement of B_s oscillations.

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arXiv2006

B -> K* gamma vs B -> rho gamma and |V_td/V_ts|

We determine |V_{\rm td}/V_{\rm ts}| = 0.192 \pm 0.016_ exp \pm 0.014_th from B -> (K^*,rho) gamma as measured by the B-factories Babar and Belle. This version differs from the original proceedings by the inclusion of the new BaBar measurement of B -> rho(omega) gamma presented at ICHEP 2006, which significantly shifts the results for |V_{td}/V_{ts}|.

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