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Mark B. Wise

Publications and source records attributed to Mark B. Wise.

At least 127 records · Page 7Linked to original sources
arXiv1998

Comment on $V_{ub}$ from Exclusive Semileptonic B and D Decays

The prospects for determining $|V_{ub}|$ from exclusive B semileptonic decay are discussed. The double ratio of form factors $(f^{B\toρ}/f^{B\to K^*})/ (f^{D\toρ}/f^{D\to K^*})$ is calculated using chiral perturbation theory. Its deviation from unity due to contributions that are non-analytic in the symmetry breaking parameters is very small. Combining experimental data obtainable from (B->rho l nu), (B->K* l l) and (D->rho l nu) can lead to a model independent determination of $|V_{ub}|$ with an uncertainty from theory of about 10%.

hep-ph↗
arXiv1998

HQET and Exclusive B Decays

Exclusive semileptonic B decays are discussed. The emphasis is on using semileptonic decays to determine |V_{ub}| and |V_{cb}|. Recent progress in our understanding of B semileptonic decays to excited charmed mesons is also reviewed.

hep-ph↗
arXiv1998

A New Expansion for Nucleon-Nucleon Interactions

We introduce a new and well defined power counting for the effective field theory describing nucleon-nucleon interactions. Because of the large NN scattering lengths it differs from other applications of chiral perturbation theory and is facilitated by introducing an unusual subtraction scheme and renormalization group analysis. Calculation to subleading order in the expansion can be done analytically, and we present the results for both the 1S0 and 3S1-3D1 channels.

nucl-th↗
arXiv1997

The b-quark and Symmetries of the Strong Interaction

Applications of HQET and NRQCD to fragmentation are briefly reviewed. The special role of the b-quark in applications of heavy quark symmetry is discussed. Predictions of HQET for semileptonic B decays to excited charmed mesons are considered.

hep-ph↗
arXiv1997

Semileptonic B decays to excited charmed mesons

Exclusive semileptonic B decays into excited charmed mesons are investigated at order $Λ_{QCD}/m_Q$ in the heavy quark effective theory. Differential decay rates for each helicity state of the four lightest excited $D$ mesons ($D_1$, $D_2^*$, $D_0^*$, and $D_1^*$) are examined. At zero recoil, $Λ_{QCD}/m_Q$ corrections to the matrix elements of the weak currents can be written in terms of the leading Isgur-Wise functions for the corresponding transition and meson mass splittings. A model independent prediction is found for the slope parameter of the decay rate into helicity zero $D_1$ at zero recoil. The differential decay rates are predicted, including $Λ_{QCD}/m_Q$ corrections with some model dependence away from zero recoil and including order $α_s$ corrections. Ratios of various exclusive branching ratios are computed. Matrix elements of the weak currents between $B$ mesons and other excited charmed mesons are discussed at zero recoil to order $Λ_{QCD}/m_Q$. These amplitudes vanish at leading order, and can be written at order $Λ_{QCD}/m_Q$ in terms of local matrix elements. Applications to $B$ decay sum rules and factorization are presented.

hep-ph↗
arXiv1997

Recent Progress in Effective Field Theory

Applications of effective field theory to nucleon-nucleon scattering, quarkonia decay and production and B meson decay are discussed. Some unresolved issues are considered.

hep-ph↗
arXiv1997

Kinematic Enhancement of Non-Perturbative Corrections to Quarkonium Production

In this letter we address issues involved in quarkonium production near the boundaries of phase space. It is shown that higher-order non-perturbative contributions are enhanced in this kinematic region and lead to a breakdown of the non-relativistic (NRQCD) expansion. This breakdown is a consequence of sensitivity to the kinematics of soft gluon radiation and to the difference between partonic and hadronic phase space. We show how these large corrections can be resummed giving the dominant contribution to the cross section. The resummation leads to the introduction of non-perturbative, universal distribution functions. We discuss the importance of these shape functions for several observables, in particular the energy distribution of photo-produced $J/ψ$ close to the endpoint.

hep-ph↗
arXiv1997

V_{ub} from the Hadronic Invariant Mass Spectrum in Semileptonic B Decay

The hadronic invariant mass spectrum for the inclusive charmless semileptonic decay $B\to X_u e \barν_e$ is studied. Particular attention is paid to the region $s_H<m_D^2$, which may be useful for extracting the value of $|V_{ub}|$. The sensitivity of the spectrum to the parameter $\barΛ\equiv m_B - m_b$ is explored. Perturbative QCD corrections to $dΓ/ds_H$ of order $α_s^2β_0$ are calculated. For $s_H \sim \barΛm_b$ nonperturbative QCD effects are important and the shape of the invariant mass spectrum is controlled by the B meson matrix element of an infinite sum of local operators. The utility of the hadronic mass spectrum for extracting $|V_{ub}|$ is explored.

hep-ph↗
arXiv1997

Comment on nonperturbative effects in $B\to X_sγ$

Uncertainties in the theoretical prediction for the inclusive $B\to X_sγ$ decay rate are discussed. We emphasize that there is no operator product expansion for this process. Nonetheless, some nonperturbative effects involving a virtual $c\bar c$ loop are calculable using the operator product expansion. They give a contribution to the decay rate that involves the B meson matrix element of an infinite tower of operators. The higher dimension operators give effects that are only suppressed by powers of $m_bΛ_{QCD}/m_c^2 \sim 0.6$, but come with small coefficients.

hep-ph↗
arXiv1997

Connections Between Inclusive and Exclusive Semileptonic B Decay

B decay sum rules relate exclusive B semileptonic decay matrix elements to forward B-meson matrix elements of operators in HQET. At leading order the operators that occur are the b-quark kinetic energy $λ_1$ and chromomagnetic energy $λ_2$. The latter is determined by the measured $B^*-B$ mass splitting. The derivation of these sum rules is reviewed and perturbative QCD corrections are discussed. A determination of $λ_1$ and the energy of the light degrees of freedom in a B-meson, $\barΛ$, from semileptonic B decay data is presented. Future prospects for improving these sum rules are discussed.

hep-ph↗
arXiv1997

Model independent results for $B\to D_1(2420)\ell\barν$ and $B\to D_2^*(2460)\ell\barν$ at order $Λ_{QCD}/m_{c,b}$

Exclusive semileptonic B decays into $D_1$ and $D_2^*$ mesons are investigated including order $Λ_{QCD}/m_{c,b}$ corrections using the heavy quark effective theory. At zero recoil, the $Λ_{QCD}/m_{c,b}$ corrections can be written in terms of the leading Isgur-Wise function for these transitions, $τ$, and known meson mass splittings. We obtain an almost model independent prediction for the shape of the spectrum near zero recoil, including order $Λ_{QCD}/m_{c,b}$ corrections. We determine $τ(1)$ from the measured $B\to D_1\ell\barν$ branching ratio. Implications for B decay sum rules are discussed.

hep-ph↗
arXiv1996

Corrections to the Bjorken and Voloshin sum rules

We calculate near zero recoil the order $α_s$ corrections to the Bjorken and Voloshin sum rules that bound the $B\to D^{(*)}\ell\barν$ form factors. These bounds are derived by relating the result of inserting a complete set of physical states in a time ordered product of weak currents to the operator product expansion. The sum rules sum over physical states with excitation energies less than a scale $Δ$. We find that the corrections to the Bjorken bound are moderate, while the Voloshin bound receives sizable corrections enhanced by $Δ/Λ_{QCD}$. With some assumptions, we find that the slope parameter for the form factor $h_{A_1}$ in $B\to D^*\ell\barν$ decay satisfies $0.4\lesssimρ_{A_1}^2 \lesssim 1.3$.

hep-ph↗
arXiv1996

Nucleon-Nucleon Scattering from Effective Field Theory

We perform a nonperturbative calculation of the 1S0 NN scattering amplitude using an effective field theory (EFT) expansion. The expansion we advocate is a modification of what has been used previously; it is no a chiral expansion in powers of the pion mass. We use dimensional regularization throughout and the MS-bar subtraction scheme; our final result depends only on physical observables. We show that the EFT expansion of the quantity |p|cot delta(p) converges at momenta much greater than the scale that characterizes the derivative expansion of the EFT Lagrangian. Our conclusions are optimistic about the applicability of an EFT approach to the quantitative study of nuclear matter.

nucl-th↗
arXiv1996

Implications of the $B \to X \ell \barν_\ell$ lepton spectrum for heavy quark physics

The shape of the lepton spectrum in inclusive semileptonic $B\to X\,\ell\,\barν_\ell$ decay is sensitive to matrix elements of the heavy quark effective theory, $\barΛ$ and $λ_1$. From CLEO data we extract $\barΛ=0.39\pm0.11\,$GeV and $λ_1=-0.19\pm0.10\,{\rm GeV}^2$, where the uncertainty is the $1σ$ statistical error only. Systematic uncertainties are discussed. These values for $\barΛ$ and $λ_1$ are used to determine $|V_{cb}|$ and the $\overline{\rm MS}$ bottom and charm quark masses. We discuss the theoretical uncertainties related to order $(Λ_{\rm QCD}/m_b)^3$ effects and higher orders in the perturbative expansion.

hep-ph↗
arXiv1996

An Elusive Z' Coupled to Beauty

By extending the standard gauge group to SU(3)_c \times SU(2)_L \times U(1)_Y \times U(1)_X with X charges carried only by the third family we accommodate the LEP measurement of R_b and predict a potentially measurable discrepancy in A_{FB}^{b} in e^+e^- scattering and that D^0\bar{D}^0 mixing may be near its experimental limit. The Z', which explicitly violates the GIM mechanism, can nevertheless be naturally consistent with FCNC constraints. Direct detection of the Z' is possible but challenging.

hep-ph↗
arXiv1996

Perturbative corrections to zero recoil inclusive $B$ decay sum rules

Comparing the result of inserting a complete set of physical states in a time ordered product of $b$ decay currents with the operator product expansion gives a class of zero recoil sum rules. They sum over physical states with excitation energies less than $Δ$, where $Δ$ is much greater than the QCD scale and much less than the heavy charm and bottom quark masses. These sum rules have been used to derive an upper bound on the zero recoil limit of the $B\to D^*$ form-factor, and on the matrix element of the kinetic energy operator between $B$ meson states. Perturbative corrections to the sum rules of order $α_s(Δ) Δ^2/m_{c,b}^2$ have previously been computed. We calculate the corrections of order $α_s(Δ)$ and $α_s^2(Δ) β_0$ keeping all orders in $Δ/m_{c,b}$, and show that these perturbative QCD corrections suppressed by powers of $Δ/m_{c,b}$ significantly weaken the upper bound on the zero recoil $B\to D^*$ form-factor, and also on the kinetic energy operator's matrix element.

hep-ph↗
arXiv1995

$|V_{ub}|$ from exclusive $B$ and $D$ decays

We propose a model-independent method to determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{ub}|$ from exclusive $B$ and $D$ decays. Combining information obtainable from $B\to ρ\ell\barν_\ell$, $B\to K^*ν\barν$, $D\to ρ\bar\ellν_\ell$ and $D\to K^*\bar\ellν_\ell$, a determination of $|V_{ub}|$ is possible, with an uncertainty from theory of around 10\%. Theoretical uncertainties in the $B\to K^*\ell\bar\ell$ decay rate are discussed.

hep-ph↗