arXiv subjects

Alexey A. Petrov

Publications and source records attributed to Alexey A. Petrov.

At least 73 records · Page 4Linked to original sources

arXiv2004

The $D^0 - \bar D^0$ mass difference from a dispersion relation

We study the Standard Model prediction for the mass difference between the two neutral D meson mass eigenstates, $Δm$. We derive a dispersion relation based on heavy quark effective theory that relates $Δm$ to an integral of the width difference of heavy mesons, $ΔΓ$, over varying values of the heavy meson mass. Modeling the $m_D$-dependence of certain D decay partial widths, we investigate the effects of SU(3) breaking from phase space on the mass difference. We find that $Δm$ may be comparable in magnitude to $ΔΓ$ in the Standard Model.

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arXiv2003

Charm physics: theoretical review

We review recent developments in charm physics, focusing on the physics of charmed mesons. We discuss charm spectroscopy, decay constants, as well as searches for new physics with charmed mesons. We discuss D0-anti-D0 mixing and CP-violation in charm decays. We also present the modified Nelson plot of charm mixing predictions.

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arXiv2003

Comment on the new $D_s^{(*)+} π^0$ resonances

We propose an explanation of the new resonances observed in $D_s^{(*)+} π^0$ decays. We suggest that the data can be explained by the mixing of conventional p-wave excited $D_s^+$ mesons with 4-quark states. The narrow states observed in $D_s^+ π^0$ and $D_s^{*+}π^0$ are primarily p-wave $D_{sJ}^{*}$ states, while the predominantly 4-quark states are shifted above $D^{(*)} K$ threshold and should be broad. Ranges for the mixing parameter and mass of the 4-quark state in this scenario are given. Other experimental consequences are discussed.

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arXiv2003

Lambda_b lifetime puzzle in heavy-quark expansion

Lifetime differences of heavy hadrons can be consistently computed in heavy-quark expansion. The leading effects appear through spectator interactions at order 1/m_b^3. We compute a well-defined subset of 1/m_b^4 corrections to the lifetime ratio of Lambda_b baryon and B_d meson. We find that these corrections are large and should be taken into account in the systematic analysis of heavy hadron lifetimes. We claim that they could shift the ratio τ_{Λ_b}/τ_{B_d} by as much as -4.5%, significantly reducing the discrepancy between the theoretical predictions and experimental observations.

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arXiv2003

Charm Phenomenology for CKM Parameters

We review several key aspects of charm phenomenology which are important for the general program of determination of matrix elements of the Cabbibo-Kobayashi-Maskava (CKM) matrix. We argue that charm physics plays an important role in reducing uncertainties in non-perturbative QCD parameters whose values are required for understanding of underlying quark-level processes. We also review the current status of searches for new physics in mixing and CP violation in charmed mesons both at the currently operating and proposed facilities.

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arXiv2002

Lifetime Differences in Heavy Mesons With Time Independent Measurements

Heavy meson pairs produced in the decays of heavy quarkonium resonances at e+ e- machines (beauty and tau-charm factories) have the useful property that the two mesons are in the CP-correlated states. By tagging one of the mesons as a CP eigenstate, a lifetime difference of heavy neutral meson mass eigenstates width difference may be determined by measuring the leptonic branching ratio of the other meson. We discuss the use of this and related methods both in the case where time dependent mixing is small and when it is significant. We consider the impact of possible CP-violating effects and present the complete results for CP-entangled decay rates with CP-violation taken into account.

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arXiv2002

D0-anti-D0 mixing

The Standard Model contribution to D0-anti-D0 mixing is dominated by the contributions of light s and d quarks. Neglecting the tiny effects due to b quark, both mass and lifetime differences vanish in the limit of SU(3) symmetry. Thus, the main challenge in the Standard Model calculation of the mass and width difference in the D0-anti-D0 system is to estimate the size of SU(3) breaking effects. We prove that D meson mixing occurs in the Standard Model only at second order in SU(3) violation. We consider the possibility that phase space effects may be the dominant source of SU(3) breaking. We find that y=Delta Gamma/2Gamma of the order of one percent is natural in the Standard Model, potentially reducing the sensitivity to new physics of measurements of D meson mixing. We also discuss the possibility of observing lifetime differences and CP violation in charmed mesons both at the currently operating and proposed facilities.

hep-ph↗

arXiv2001

SU(3) Breaking and D0-D0bar Mixing

The main challenge in the Standard Model calculation of the mass and width difference in the D0-D0bar system is to estimate the size of SU(3) breaking effects. We prove that D meson mixing occurs in the Standard Model only at second order in SU(3) violation. We consider the possibility that phase space effects may be the dominant source of SU(3) breaking. We find that y=(Delta Gamma)/(2Gamma) of the order of one percent is natural in the Standard Model, potentially reducing the sensitivity to new physics of measurements of D meson mixing.

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arXiv2001

Comments on Color-Suppressed Hadronic B Decays

Recent experimental results on the color-suppressed nonleptonic decays B^0 -> D^{(*)0} pi^0 provide evidence for a failure of the naive factorization model and for sizeable relative strong-interaction phases between class-1 and class-2 B -> D^(*) pi decay amplitudes. The allowed regions for the corresponding ratios of (complex) isospin amplitudes and a_2/a_1 parameters are determined. The results are interpreted in the context of QCD factorization for the related class-1 amplitudes in the heavy-quark limit.

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arXiv2001

Two-Loop Renormalization of Heavy--Light Currents at Order 1/m_Q in the Heavy-Quark Expansion

We present exact results, at next-to-leading order in renormalization-group improved perturbation theory, for the Wilson coefficients appearing at order 1/m_Q in the heavy-quark expansion of heavy-light current operators. To this end, we complete the calculation of the corresponding two-loop anomalous dimension matrix. Our results are important for determinations of |V_{ub}| using exclusive and inclusive semileptonic B decays. They are also relevant to computations of the decay constant f_B based on a heavy-quark expansion.

hep-ph↗

arXiv2000

Effects from the charm scale in K+ -> pi+ nu nubar

We consider contributions to the rare decay K+ -> pi+ nu nubar which become nonlocal at the charm scale. Compared to the leading term, such amplitudes are suppressed by two powers of mK/mc and could potentially give corrections at the level of 15%. We compute the leading coefficients of the subleading dimension eight operators in the effective theory below the charm mass. The matrix elements of these operators cannot all be calculated from first principles and some must be modeled. We find that these contributions are likely to be small, but the estimate is sufficiently uncertain that the result may be as large as the existing theoretical uncertainty from other sources.

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arXiv2000

Lessons from CLEO and FOCUS Measurements of D0-anti-D0 Mixing Parameters

If the true values of the D0-anti-D0 mixing parameters lie within the one sigma ranges of recent measurements, then there is strong evidence for a large width difference, y > 0.01, and large SU(3) breaking effects in strong phases, δ> pi/4. These constraints are model independent, and would become stronger if M_{12}/Gamma_{12} << 1 in the D0-anti-D0 system. The interesting fact that the FOCUS result cannot be explained by a large mass difference is not trivial and depends on the small D0-anti-D0 production asymmetry in FOCUS and the bounds on CP violating effects from CLEO. The large value of δmight help explain why y ~ sin^2(theta_c).

hep-ph↗

arXiv2000

Measuring gamma cleanly with CP-tagged Bs and Bd decays

We propose a new method for measuring the CKM phase gamma using the partial rates for CP-tagged Bs decays. Such an experiment could be performed at a very high luminosity symmetric e+e- collider operating at the Upsilon(5S) resonance, where the Bs-Bsbar state is produced in a state of definite CP. We also discuss CP-tagging in the Bd system at the Upsilon(4S), where a time-dependent analysis is required to compensate for the anticipated large CP violation in Bd-Bdbar mixing.

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arXiv2000

The use of neutrino beams from muon storage rings

I give a brief overview of the physics potential of short baseline experiments at neutrino factories, i.e. facilities providing high energy and high intensity neutrino beams, like the one planned to be built in connection with the proposed high energy muon storage ring. These facilities would offer a unique opportunity to perform new precision studies of QCD and electroweak interactions. New types of measurements, such as studies of gluon density of the nucleon via charmonium production and extractions of V_cb and V_ub CKM matrix elements, will become possible. Interesting new physics scenarios can also be explored.

hep-ph↗

arXiv1999

Strong phases and D0-anti-D0 mixing parameters

We argue that there could be large, SU(3) violating resonance contributions to D -> K pi decays which would affect the extraction of the D0-anti-D0 mixing parameters from experiment. Such contributions can induce a large strong phase in the interference between the doubly Cabibbo suppressed and the mixing induced Cabibbo favored contributions to the D0 -> K^+ pi^- and anti-D0 -> K^- pi^+ decays. Consequently, the interpretation of a large, CP conserving interference term can involve a large mass difference Delta M rather than a large width difference Delta Gamma.

hep-ph↗

arXiv1999

Measuring V_ub in Inclusive B Decays to Charm

We propose a novel method of measuring the CKM matrix element V_ub, via inclusive B decays to "wrong sign" charm. This process is mediated by the quark level decay b -> u cbar s'. When normalized to the inclusive semileptonic decay rate, the theoretical expression is very well behaved, with small uncertainties from unknown quark masses and no leading renormalon ambiguity. We compute the decay rate for this process, including the leading perturbative and nonperturbative corrections.

hep-ph↗

arXiv1999

Final state interactions: from strangeness to beauty

I give a brief review of final state interactions in meson decays. I describe possible effects of FSI in K, D and B systems, paying particular attention to the description of the heavy meson decays. Available theoretical methods for dealing with the effects of FSI are discussed.

hep-ph↗

arXiv1999

Phenomenology of V_ub from Ratios of Inclusive B Decay Rates

We explore the theoretical feasibility of extracting V_ub from two ratios built from B meson inclusive partial decays, R_1 = Gamma(b-> u cbar s)/3Gamma(b -> c l nu), and R_2 = [Gamma(b -> c X) - Gamma(b -> cbar X)]/Gamma(b -> c ubar d). We discuss contributions to these quantities from perturbative and nonperturbative physics, and show that they can be computed with overall uncertainties at the level of 10%.

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