arXiv subjects

Patricia Ball

Publications and source records attributed to Patricia Ball.

At least 55 records · Page 3Linked to original sources

arXiv2000

Spontaneous CP Violation in the Left-Right-Symmetric Model

We investigate the pattern of CP violation in \Kd, \Bd and \Bs mixing in a symmetrical \model model with spontaneous CP violation. Performing a careful analysis of all relevant restrictions on the model's parameters from $ΔM_K$, $ΔM_{B_d}$, $ΔM_{B_s}$, $ε_K$, the sign of \ee and the mixing-induced CP asymmetry in \goldd, we find that the mass of the right-handed charged gauge-boson, $M_2$, is restricted to be in the range 2.75 to 13$ $TeV, and that the mass of the flavour-changing neutral-Higgs bosons, $M_H$, must be between 10.2 to 14.6$ $TeV. We also find that the model, although still compatible with present experimental data, cannot accomodate the SM prediction of large CP violation in \goldd, but, on the other hand, predicts a large CP-asymmetry of ${\cal O}(40%)$ in \golds. These specific predictions make it possible to submit the model to a scrupulous test at B factories and hadron colliders.

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arXiv1999

An Analysis of B_s Decays in the Left-Right-Symmetric Model with Spontaneous CP Violation

Non-leptonic B_s decays into CP eigenstates that are caused by \bar b -> \bar cc\bar s quark-level transitions, such as B_s -> D_s^+D^-_s, J/psi eta^(') or J/psi phi, provide a powerful tool to search for ``new physics'', as the CP-violating effects in these modes are tiny in the Standard Model. We explore these effects for a particular scenario of new physics, the left-right-symmetric model with spontaneous CP violation. In our analysis, we take into account all presently available experimental constraints on the parameters of this model, i.e. those implied by K- and B-decay observables; we find that CP asymmetries as large as O(40%) may arise in the B_s channels, whereas the left-right-symmetric model favours a small CP asymmetry in the ``gold-plated'' mode B_d -> J/psi K_S. Such a pattern would be in favour of B-physics experiments at hadron machines, where the B_s modes are very accessible.

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arXiv1999

A Comparative Study of the Decays $B \to (K,K^*) \ell^+ \ell^-$ in Standard Model and Supersymmetric Theories

Using improved theoretical calculations of the decay form factors in the Light Cone-QCD sum rule approach, we investigate the decay rates, dilepton invariant mass spectra and the forward-backward (FB) asymmetry in the decays $B \to (K,K^*) \ell^+ \ell^-$ ($\ell^\pm =e^\pm,μ^\pm,τ^\pm$) in the standard model (SM) and a number of popular variants of the supersymmetric (SUSY) models. Theoretical precision on the differential decay rates and FB-asymmetry is estimated in these theories taking into account various parametric uncertainties. We show that existing data on $B \to X_s γ$ and the experimental upper limit on the branching ratio ${\cal B}(B \to K^* μ^+ μ^-)$ provide interesting bounds on the coefficients of the underlying effective theory. We argue that the FB-asymmetry in $B \to K^* \ell^+ \ell^-$ constitutes a precision test of the SM and its measurement in forthcoming experiments may reveal new physics. In particular, the presently allowed large-$\tan β$ solutions in SUGRA models, as well as more general flavor-violating SUSY models, yield FB-asymmetries which are characteristically different from the corresponding ones in the SM.

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arXiv1999

Anatomy of Mixing-Induced CP Asymmetries in Left-Right-Symmetric Models with Spontaneous CP Violation

We investigate the pattern of CP violation in K, B_d and B_s mixing in a symmetrical SU(2)_R x SU(2)_L x U(1) model with spontaneous CP violation. We calculate the phases of the left and right quark mixing matrices beyond the small phase approximation and perform a careful analysis of all relevant restrictions on the model's parameters from Delta m_K, Delta m_B, epsilon, epsilon'/epsilon and the CP asymmetry in B->J/psi K_S. We find that, with current experimental data, the mass of the right-handed charged gauge boson, M2, is restricted to be in the range 2.75 to 13 TeV and the mass of the flavour-changing neutral Higgs boson, MH, in 10.2 to 14.6 TeV. This means in particular that the decoupling limit M2, MH -> infinity is already excluded by experiment. We also find that the model favours opposite signs of epsilon and sin 2beta and is excluded if sin 2beta > 0.1.

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arXiv1998

Theoretical Update of Pseudoscalar Meson Distribution Amplitudes of Higher Twist: The Nonsinglet Case

We discuss the two and three particle light-cone distribution amplitudes (DAs) of pseudoscalar nonsinglet mesons of twist 3 and 4. Using nonlocal operator identities and conformal expansion, we derive closed expressions for several DAs. We also include meson-mass corrections which prove to be dominant in the twist 4 DAs of K and eta mesons. Explicit parametrizations for the DAs of pi, K and eta mesons are given, with the numerical input parameters determined from QCD sum rules.

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arXiv1998

Higher Twist Distribution Amplitudes of Vector Mesons in QCD: Twist-4 Distributions and Meson Mass Corrections

We present a systematic study of twist-4 light-cone distribution amplitudes of vector mesons in QCD, which is based on conformal expansion. The structure of meson mass corrections is studied in detail. A complete set of distribution amplitudes is constructed, which satisfies all (exact) equations of motion and constraints from conformal expansion. Nonperturbative input parameters are estimated from QCD sum rules. Our study suggests that meson mass corrections may present a dominant source of higher twist effects in exclusive processes.

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arXiv1998

Handbook of Higher Twist Distribution Amplitudes of Vector Mesons in QCD

We give a summary of existing results on higher twist distribution amplitudes of vector mesons in QCD. Special attention is payed to meson mass corrections which turn out to be large. A ``shopping list'' is presented of most important nonperturbative parameters which enter distribution amplitudes.

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arXiv1998

Exclusive Semileptonic and Rare B-Meson Decays in QCD

We present the first complete results for the semileptonic and rare radiative form factors of B-mesons weak decay into a light vector-meson (rho, omega, K*, phi) in the light-cone sum-rule approach. The calculation includes radiative corrections, higher-twist corrections and SU(3)-breaking effects. The theoretical uncertainty is investigated in detail. A simple parametrization of the form factors is given in terms of three parameters each. We find that the form factors observe several relations inspired by heavy-quark symmetry.

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arXiv1998

B->pi and B->K Transitions from QCD Sum Rules on the Light-Cone

I calculate the form factors describing semileptonic and penguin-induced decays of B mesons into light pseudoscalar mesons. The form factors are calculated from QCD sum rules on the light-cone including contributions up to twist 4, radiative corrections to the leading twist contribution and SU(3)-breaking effects. The theoretical uncertainty is estimated to be \sim 15%. The heavy-quark-limit relations between semileptonic and penguin form factors are found to be valid in the full accessible range of momentum transfer.

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arXiv1998

Higher Twist Distribution Amplitudes of Vector Mesons in QCD: Formalism and Twist Three Distributions

We present a systematic study of twist three light-cone distribution amplitudes of vector mesons in QCD, which is based on conformal expansion and takes into account meson and quark mass corrections. A complete set of distribution amplitudes is constructed for rho, omega, K* and phi mesons, which satisfies all (exact) equations of motion and constraints from conformal expansion. Nonperturbative input parameters are calculated from QCD sum rules, including an update of SU(3) breaking corrections in the leading twist distributions.

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arXiv1998

B decays into light mesons

I calculate the form factors describing semileptonic and penguin induced decays of B mesons into light pseudoscalar and vector mesons. The form factors are calculated from QCD sum rules on the light-cone including contributions up to twist 4, radiative corrections to the leading twist contribution and SU(3) breaking effects. The theoretical uncertainty is estimated to be $\sim$ (15-20)%.

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arXiv1997

The most promising ways to measure V_ub

I review currently discussed methods to determine the CKM mixing matrix element $|V_{ub}|$ from experimental data. Although the theory of inclusive decays and their spectra has entered a model-independent stage, its predictions are still sensitive to various input parameters, in particular the poorly known $b$ quark mass. At present, determinations from exclusive channels, notably $B\toπe ν$, seem slightly more accurate and allow determination of $|V_{ub}|$ from the spectrum in the momentum transfer to the leptons with a theoretical uncertainty of $\sim 10%$.

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arXiv1997

Use and Misuse of QCD Sum Rules in Heavy-to-light Transitions: the Decay $B\toρe ν$ Reexamined

The existing calculations of the form factors describing the decay $B\toρe ν$ from QCD sum rules have yielded conflicting results at small values of the invariant mass squared of the lepton pair. We demonstrate that the disagreement originates from the failure of the short-distance expansion to describe the $ρ$ meson distribution amplitude in the region where almost the whole momentum is carried by one of the constituents. This limits the applicability of QCD sum rules based on the short-distance expansion of a three-point correlation function to heavy-to-light transitions and calls for an expansion around the light-cone, as realized in the light-cone sum rule approach. We derive and update light-cone sum rules for all the semileptonic form factors, using recent results on the $ρ$ meson distribution amplitudes. The results are presented in detail together with a careful analysis of the uncertainties, including estimates of higher-twist effects, and compared to lattice calculations and recent CLEO measurements. We also derive a set of ``improved'' three-point sum rules, in which some of the problems of the short-distance expansion are avoided and whose results agree to good accuracy with those from light-cone sum rules.

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arXiv1996

The Exclusive Decay $B\toρe ν$ Beyond Model Calculations

Due to its comparatively theoretical ``simplicity'', the decay channel $B\toρe ν$ offers one of the best possibilities to determine the CKM matrix element $|V_{ub}|$ accurately. I present a new calculation of the relevant hadronic form factors from light-cone sum rules. I also review the results from lattice calculations and find that they agree with the results from light-cone sum rules where comparison is possible.\\ This paper relies on work done in collaboration with V.M.\ Braun.

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arXiv1996

Theoretical Update of the Semileptonic Branching Ratio of B Mesons

We reconsider the prediction of the semileptonic branching ratio of B mesons, using a recent calculation of the radiative corrections with account for finite quark masses in nonleptonic decays and taking into account 1/m_b^2 corrections. For the semileptonic branching ratio we obtain B_SL =(11.8\pm 1.6)% using pole quark masses and B_SL = (11.0\pm 1.9)% using running MS-bar quark masses. The uncertainty is dominated by unknown higher order perturbative corrections. We conclude that the present accuracy of the theoretical analysis does not allow to state a significant disagreement with the experimental results. However, our re-analysis of the decay b->ccs yields an increase of (35\pm 11)% due to next-to-leading order corrections including mass dependent terms, which further emphasizes the problem of the average charm quark content of the final states in B decays. Abstract of the erratum: Some of the numerical results presented in our paper PLB 342 (1995) 362 are affected by an error in the computer program and need to be revised. The numerical changes are, however, marginal. We take the opportunity to incorporate the complete results for the quark mass dependence of the radiative corrections to the subprocess b->ccs and enlarge the discussion of the average charm quark content in the final state, giving the results in two different renormalization schemes and adding a figure with charm quark content plotted vs. the semileptonic branching ratio.

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arXiv1995

Phenomenological Evidence for the Gluon Content of $η$ and $η'$

We discuss the effect of $η$--$η'$ mixing and of axial current anomalies on various decay processes. We describe the 2$γ$ decays of $η$ and $η'$, the radiative decays of low-lying vector mesons as well as the decays $η\to 3π$, $J/ψ\toηγ$ and $J/ψ\toη'γ$ in one unified framework, in which they are related to the electromagnetic and strong axial current anomalies, respectively. We also discuss briefly the enhancement of $η'$ in $D_s$ decays and suggest a possible relation to gluon-mediated processes. The importance of the decays of the glueball candidates $f_0(1500)$ and $ f_0(1590)$ into $ηη'$ channels is also stressed.

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arXiv1995

$|V_{cb}|$ from inclusive semileptonic B decays

We determine $|V_{cb}|$ from inclusive semileptonic B decays including resummation of supposedly large perturbative corrections, which originate from the running of the strong coupling. We argue that the low value of the BLM scale found previously for inclusive decays is a manifestation of the renormalon divergence of the perturbative series starting already in third order. A reliable determination of $|V_{cb}|$ from inclusive decays is still possible if one uses a short-distance b quark mass. We find that using the $\overline{\rm MS}$ running mass significantly reduces the perturbative coefficients already in low orders. For a semileptonic branching ratio of $10.9\%$ we obtain $|V_{cb}|(τ_B/1.50\,{\rm ps})^{1/2}=0.041\pm 0.002\pm 0.002$. This work was done in collaboration with M. Beneke and V.M.\ Braun.

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arXiv1995

Next-to-leading Order Radiative Corrections to the Decay $b\to ccs$

We calculate the complete ${\cal O}(α_s)$ corrections to the quark decay $b\to ccs$ taking full account of the quark masses, but neglecting penguin contributions. For a c to the b quark mass ratio $m_c/m_b= 0.3$ and a strange quark mass of $0.2\,$GeV, we find that the next-to-leading order (NLO) corrections increase $Γ(b\to ccs)$ by $(32\pm 15)\%$ with respect to the leading order expression, where the uncertainty is mostly due to scale- and scheme-dependences. Combining this result with the known NLO and non-perturbative corrections to other B meson decay channels we obtain an updated value for the semileptonic branching ratio of B mesons, $B_{SL}$, of $(12.0\pm 1.4)\% $ using pole quark masses and $(11.2\pm 1.7)\% $ using running $\overline{\mbox{MS}}$ masses.

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