Publications (25)3.63 Total impact
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Article: Theory of B -> K(*)l+l- decays at high q^2: OPE and quark-hadron duality
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ABSTRACT: We develop a systematic framework for exclusive rare B decays of the type B -> K(*)l+l- at large dilepton invariant mass q^2. It is based on an operator product expansion (OPE) for the required matrix elements of the nonleptonic weak Hamiltonian in this kinematic regime. Our treatment differs from previous work by a simplified operator basis, the explicit calculation of matrix elements of subleading operators, and by a quantitative estimate of duality violation. The latter point is discussed in detail, including the connection with the existence of an OPE and an illustration within a simple toy model.01/2011; -
Article: Precision Flavour Physics with $B\to K\nu\bar\nu$ and $B\to Kl^+l^-$
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ABSTRACT: We show that a combined analysis of $B\to K\nu\bar\nu$ and $B\to Kl^+l^-$ allows for new physics tests practically free of form factor uncertainties. Residual theory errors are at the level of several percent. Our study underlines the excellent motivation for measuring these modes at a Super Flavour Factory. Comment: 26 pages, 2 figures09/2009; -
Article: Penguins with Charm and Quark-Hadron Duality
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ABSTRACT: The integrated branching fraction of the process $B\to X_s l^+l^-$ is dominated by resonance background from narrow charmonium states, such as $B\to X_s\psi\to X_s l^+l^-$, which exceeds the non-resonant charm-loop contribution by two orders of magnitude. The origin of this fact is discussed in view of the general expectation of quark-hadron duality. The situation in $B\to X_s l^+l^-$ is contrasted with charm-penguin amplitudes in two-body hadronic B decays of the type $B\to\pi\pi$, for which it is demonstrated that resonance effects and the potentially non-perturbative $c\bar c$ threshold region do not invalidate the standard picture of QCD factorization. This holds irrespective of whether the charm quark is treated as a light or a heavy quark. Comment: 20 pages, 4 figures02/2009; -
Article: B, D and K decays
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ABSTRACT: With the advent of the LHC, we will be able to probe New Physics (NP) up to energy scales almost one order of magnitude larger than it has been possible with present accelerator facilities. While direct detection of new particles will be the main avenue to establish the presence of NP at the LHC, indirect searches will provide precious complementary information, since most probably it will not be possible to measure the full spectrum of new particles and their couplings through direct production. In particular, precision measurements and computations in the realm of flavour physics are expected to play a key role in constraining the unknown parameters of the Lagrangian of any NP model emerging from direct searches at the LHC. The aim of Working Group 2 was twofold: on one hand, to provide a coherent, up-to-date picture of the status of flavour physics before the start of the LHC; on the other hand, to initiate activities on the path towards integrating information on NP from high-pT and flavour data. Comment: Report of Working Group 2 of the CERN Workshop ``Flavour in the era of the LHC'', Geneva, Switzerland, November 2005 -- March 200701/2008; -
Article: B, D and K decays
European Physical Journal C 01/2008; 57:309-492. · 3.63 Impact Factor -
Article: Comment on ``B->M_1 M_2: Factorization, charming penguins, strong phases, and polarization''
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ABSTRACT: We show that the factorization formula for non-leptonic B decays to two light flavor non-singlet mesons derived by Bauer et al. in the context of soft-collinear effective theory is equivalent to the corresponding formula in the QCD factorization approach. The apparent numerical differences in the analysis of B->pi+pi data performed by these authors, as compared to previous QCD factorization analyses, can largely be attributed to the neglect of known perturbative and power corrections. Comment: Comment on hep-ph/0401188 by Bauer, Pirjol, Rothstein and Stewart; 4 pages11/2004; -
Article: CP asymmetry in flavour-specific B decays beyond leading logarithms
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ABSTRACT: We compute next-to-leading order QCD corrections to the CP asymmetry a_{fs} = Im(Gamma_{12}/M_{12}) in flavour-specific B_{d,s} decays such as B_d->X l nu or B_s->D^-_s pi^+. The corrections reduce the uncertainties associated with the choice of the renormalization scheme for the quark masses significantly. In the Standard Model we predict a^d_{fs} = -(5.0 +- 1.1)*10^{-4}. As a by-product we also obtain the width difference in the B_d system at next-to-leading order in QCD.08/2003; -
Article: Kaon physics with a high-intensity proton driver
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ABSTRACT: We study opportunities for future high-precision experiments in kaon physics using a high-intensity proton driver, which could be part of the front-end of a muon storage ring complex. We discuss in particular the rare decays $K_L\to\pi^0\nu\bar\nu$, $K^+\to\pi^+\nu\bar\nu$, $K_L\to\pi^0e^+e^-$, and lepton-flavour violating modes such as $K_L\to\mu e$ and $K\to\pi\mu e$. The outstanding physics potential and long-term interest of these modes is emphasized. We review status and prospects of current and planned experiments for the processes under consideration, and indicate possible improvements and strategies towards achieving the necessary higher sensitivity. Finally, we outline the machine requirements needed to perform these high-precision kaon experiments in the context of a muon storage ring facility.08/2001; -
Article: Phenomenology of non-standard Z couplings in exclusive semileptonic b -> s transitions
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ABSTRACT: The rare decays $B\to K^{(*)}\ell^+\ell^-$, $B\to K^{(*)}\nu\bar\nu$ and $B_s\to\mu^+\mu^-$ are analyzed in a generic scenario where New Physics effects enter predominantly via $Z$ penguin contributions. We show that this possibility is well motivated on theoretical grounds, as the $\bar sbZ$ vertex is particularly susceptible to non-standard dynamics. In addition, such a framework is also interesting phenomenologically since the $\bar sbZ$ coupling is rather poorly constrained by present data. The characteristic features of this scenario for the relevant decay rates and distributions are investigated. We emphasize that both sign and magnitude of the forward-backward asymmetry of the decay leptons in $\bar B\to \bar K^*\ell^+\ell^-$, ${\cal A}^{(\bar B)}_{FB}$, carry sensitive information on New Physics. The observable ${\cal A}^{(\bar B)}_{FB}+{\cal A}^{(B)}_{FB}$ is proposed as a useful probe of non-standard CP violation in $\bar sbZ$ couplings. Comment: Minor modifications; version to appear in Phys. Rev. D06/2000; -
Article: QCD factorization for exclusive non-leptonic B-meson decays: general arguments and the case of heavy–light final states
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ABSTRACT: We provide a rigorous basis for factorization for a large class of non-leptonic two-body B-meson decays in the heavy-quark limit. The resulting factorization formula incorporates elements of the naive factorization approach and the hard-scattering approach, but allows us to compute systematically radiative (“non-factorizable”) corrections to naive factorization for decays such as B→Dπ and B→ππ. We first discuss the factorization formula from a general point of view. We then consider factorization for decays into heavy-light final states (such as B→Dπ) in more detail, including a proof of the factorization formula at two-loop order. Explicit results for the leading QCD corrections to factorization are presented and compared to existing measurements of branching fractions and final-state interaction phases.Nuclear Physics B. 06/2000; -
Article: B decays at the LHC
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ABSTRACT: We review the prospects for B decay studies at the LHC. Comment: 112 pages, ca.90 partially bitmapped PS figures, PS with high resolution figures available from http://home.cern.ch/~pball/master.ps.gz, P. Ball, R. Fleischer, G.F. Tartarelli, P. Vikas, G. Wilkinson (convenors)03/2000; -
Article: QCD Factorization for $B\to\pi\pi$ Decays: Strong Phases and CP Violation in the Heavy Quark Limit
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ABSTRACT: We show that, in the heavy quark limit, the hadronic matrix elements that enter $B$ meson decays into two light mesons can be computed from first principles, including `non-factorizable' strong interaction corrections, and expressed in terms of form factors and meson light-cone distribution amplitudes. The conventional factorization result follows in the limit when both power corrections in $1/m_b$ and radiative corrections in $\alpha_s$ are neglected. We compute the order-$\alpha_s$ corrections to the decays $B_d\to\pi^+\pi^-$, $B_d\to\pi^0\pi^0$ and $B^+\to\pi^+\pi^0$ in the heavy quark limit and briefly discuss the phenomenological implications for the branching ratios, strong phases and CP violation. Comment: 6 pages, 1 figure05/1999; -
Article: Next-to-Leading Order QCD Corrections to the Lifetime Difference of $B_s$ Mesons
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ABSTRACT: We compute the QCD corrections to the decay rate difference in the $B_s-\bar B_s$ system, $\Delta\Gamma_{B_s}$, in the next-to-leading logarithmic approximation using the heavy quark expansion approach. Going beyond leading order in QCD is essential to obtain a proper matching of the Wilson coefficients to the matrix elements of local operators from lattice gauge theory. The lifetime difference is reduced considerably at next-to-leading order. We find $(\Delta\Gamma/\Gamma)_{B_s}=(f_{B_s}/210 MeV)^2 [0.006 B(m_b)+0.150 B_S(m_b)-0.063]$ in terms of the bag parameters $B, B_S$ in the NDR scheme. As a further application of our analysis we also derive the next-to-leading order result for the mixing-induced CP asymmetry in inclusive $b\to u\bar ud$ decays, which measures $\sin 2\alpha$. Comment: 14 pages, LaTeX, 1 figure; minor modifications of the text, improved discussion of eq. (35), all results unchanged08/1998; -
Article: The Width Difference in the
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ABSTRACT: We use the heavy quark expansion to investigate the width difference DeltaGamma Bs between the B s mass eigenstates. The corrections of O( QCD=m b ) and O(m s =m b ) to the leading order expression in the operator product expansion are derived and estimated to yield a sizable reduction of the leading result for DeltaGamma Bs by typically 30%. For completeness we also quantify small effects due to penguin operators and CKM suppressed contributions. Based on our results we discuss the prediction for (DeltaGamma=Gamma) Bs with particular emphasis on theoretical uncertainties. We find (DeltaGamma=Gamma) Bs = 0:16 +0:11 Gamma0:09 , where the large error is dominated by the uncertainty in hadronic matrix elements. An accuracy of about 10% in (DeltaGamma=Gamma) Bs should be within reach, assuming continuing progress in lattice calculations. In addition we address phenomenological issues and implications of a DeltaGamma Bs measurement for constraints on DeltaM Bs and CKM pa...06/1998; -
Article: Corrections of Order $\Lambda^2_{QCD}/m^2_c$ to Inclusive Rare B Decays
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ABSTRACT: We calculate nonperturbative ${\cal O}(\Lambda^2_{QCD}/m^2_c)$ corrections to the dilepton invariant mass spectrum and the forward-backward charge asymmetry in $B\to X_se^+e^-$ decay using a heavy quark expansion approach. The method has recently been used to estimate long-distance effects in $B\to X_s\gamma$. We generalize this analysis to the case of nonvanishing photon invariant mass, $q^2\not= 0$, relevant for the rare decay mode $B\to X_se^+e^-$. In the phenomenologically interesting $q^2$ region away from the $c\bar c$ resonances, the heavy quark expansion approach should provide a reasonable description of possible nonperturbative corrections. In particular this picture is preferable to the model-dependent approach relying on the tails of Breit-Wigner resonances, which has been employed so far in the literature to account for these effects. We find that the ${\cal O}(\Lambda^2_{QCD}/m^2_c)$ corrections to the dilepton invariant mass spectrum and to the forward-backward asymmetry in $B\to X_se^+e^-$ amount to several percent at most for $q^2/m^2_b < 0.3$ and $q^2/m^2_b > 0.6$. The ${\cal O}(\Lambda^2_{QCD}/m^2_c)$ correction to the $B\to X_s\gamma$ decay rate is also computed and found to be +3%, which agrees in magnitude with previous calculations. Finally, we comment on long-distance effects in $B\to X_s\nu\bar\nu$, which in this case are extremely suppressed due to the absence of virtual photon contributions. Comment: Latex, 15 pages, 3 figures (included)05/1997; -
Article: Width difference in the B_ {s}-B [over¯] _ {s} system
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ABSTRACT: We use the heavy quark expansion to investigate the width difference ΔΓBs between the Bs mass eigenstates. The corrections of O(ΛQCD/mb) and O(ms/mb) to the leading-order expression in the operator product expansion are derived and estimated to yield a sizable reduction of the leading result for ΔΓBs by typically 30%. For completeness we also quantify small effects due to penguin operators and CKM-suppressed contributions. Based on our results we discuss the prediction for (ΔΓ/Γ)Bs with particular emphasis on theoretical uncertainties. We find (ΔΓ/Γ)Bs=0.16-0.09+0.11, where the large error is dominated by the uncertainty in hadronic matrix elements. An accuracy of about 10% in (ΔΓ/Γ)Bs should be within reach, assuming continuing progress in lattice calculations. In addition, we address phenomenological issues and implications of a ΔΓBs measurement for constraints on ΔMBs and CKM parameters. We further consider in some detail the lifetime ratio τ(Bs)/τ(Bd) and estimate that, most likely, |τ(Bs)/τ(Bd)-1|<1%.Phys. Rev. D. 09/1996; 54(7). -
Article: Width Difference in the $B_s-\bar{B_s}$ System
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ABSTRACT: We use the heavy quark expansion to investigate the width difference $\Delta\Gamma_{B_s}$ between the $B_s$ mass eigenstates. The corrections of ${\cal O}(\Lambda_{QCD}/m_b)$ and ${\cal O}(m_s/m_b)$ to the leading order expression in the operator product expansion are derived and estimated to yield a sizable reduction of the leading result for $\Delta\Gamma_{B_s}$ by typically $30\%$. For completeness we also quantify small effects due to penguin operators and CKM suppressed contributions. Based on our results we discuss the prediction for $(\Delta\Gamma/\Gamma)_{B_s}$ with particular emphasis on theoretical uncertainties. We find $(\Delta\Gamma/\Gamma)_{B_s}=0.16^{+0.11}_{-0.09}$, where the large error is dominated by the uncertainty in hadronic matrix elements. An accuracy of about $10\%$ in $(\Delta\Gamma/\Gamma)_{B_s}$ should be within reach, assuming continuing progress in lattice calculations. In addition we address phenomenological issues and implications of a $\Delta\Gamma_{B_s}$ measurement for constraints on $\Delta M_{B_s}$ and CKM parameters. We further consider in some detail the lifetime ratio $\tau(B_s)/\tau(B_d)$ and estimate that, most likely, $|\tau(B_s)/\tau(B_d)-1|<1\%$.05/1996; -
Article: The $B_c$ Meson Lifetime
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ABSTRACT: We investigate the total inclusive decay rate of the (ground state) $B_c$ meson within the framework of an operator product expansion in inverse powers of the heavy quark masses and subsequent matching onto nonrelativistic QCD. The expansion is organized as a series in the strong coupling and in powers of the heavy quark velocities in the $B_c$, reflecting the nonrelativistic nature of a heavy-heavy bound state. In this aspect the character of the expansion differs from the more familiar case of heavy-light mesons. The framework incorporates systematically corrections to the leading $b$- and $c$-quark decays due to binding effects, as well as contributions from weak annihilation and Pauli interference. Based on this approach we find for the $B_c$ meson lifetime $\tau_{B_c}=(0.4 - 0.7)\,$ps, the dominant mechanism being the decay of the charm constituent.02/1996; -
Article: Parity Violating Longitudinal Muon Polarization in $K^+\to\pi^+\mu^+\mu^-$ Beyond Leading Logarithms
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ABSTRACT: We generalize the existing analyses of the parity violating muon polarization asymmetry $\Delta_{LR}$ in $K^+\to\pi^+\mu^+\mu^-$ beyond the leading logarithmic approximation. The inclusion of next--to--leading QCD corrections reduces the residual dependence on the renormalization scales, which is quite pronounced in the leading order. This leads to a considerably improved accuracy in the perturbative calculation of the short distance dominated quantity $\Delta_{LR}$. Accordingly this will also allow to obtain better constraints on the Wolfenstein parameter $\varrho$ from future measurements of $\Delta_{LR}$. For $-0.25\leq \varrho \leq 0.25$, $V_{cb}=0.040\pm 0.004$ and $m_t=(170\pm 20)GeV$ we find $3.0\cdot 10^{-3}\leq |\Delta_{LR}|\leq 9.6\cdot 10^{-3}$. Comment: 9 pages, MPI-PhT/94-43, TUM-T31-65/9407/1994; -
Article: The Rare Decays $K^+\to\pi^+\nu\bar\nu$\ and $K_L\to\mu^+\mu^-$\ Beyond Leading Logarithms
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ABSTRACT: We analyze the branching ratio for the FCNC mode $K^+\to\pi^+\nu\bar\nu$\ in the standard model with QCD effects taken into account consistently to next-to-leading order. This involves a two-loop renormalization group analysis for the charm contribution, presented in this paper, and the calculation of $O(\alpha_s)$ corrections to all orders in $m_t/M_W$ for the top-quark case that we have described elsewhere. The inclusion of next-to-leading corrections reduces considerably the theoretical uncertainty due to the choice of the renormalization scales, inherent in any calculation to finite order in perturbation theory. For $K^+\to\pi^+\nu\bar\nu$\ this point has not been discussed previously. In particular, the related uncertainty in the determination of $|V_{td}|$ from $B(K^+\to\pi^+\nu\bar\nu)$ is reduced from $\sim 30\%$ to $\sim 7\%$ for typical values of the parameters. Simultaneously also the dependence of $B(K^+\to\pi^+\nu\bar\nu)$ on the choice of $m_c$ is considerably reduced. We also give the next-to-leading order expression for the short-distance part of $K_L\to\mu^+\mu^-$. Impacts of our calculations on the determination of the unitarity triangle are presented. Comment: 40, MPI-Ph/93-4408/1993;
Top co-authors
Top Journals
Institutions
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2004
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Ludwig-Maximilians-Universität München
- Arnold Sommerfeld Center for Theoretical Physics (ASC)
München, Bavaria, Germany
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2000
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Cornell University
New York City, NY, USA
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1996
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Fermi National Accelerator Laboratory (Fermilab)
- Theoretical Physics Department
Winfield, IL, USA
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