arXiv subjects

Mark B. Wise

Publications and source records attributed to Mark B. Wise.

At least 145 records · Page 8Linked to original sources

arXiv1995

Chiral Perturbation Theory for $τ\to ρπν_τ$, $τ\to K^* πν_τ$, and $τ\to ωπν_τ$

We use heavy vector meson $SU(2)_L \times SU(2)_R$ chiral perturbation theory to predict differential decay distributions for $τ\rightarrow ρπν_τ$ and $τ\rightarrow K^* πν_τ$ in the kinematic region where $p_V \cdot p_π/m_V$ (here $V = ρ$ or $K^*$) is much smaller than the chiral symmetry breaking scale. Using the large number of colors limit we also predict the rate for $τ\rightarrow ωπν_τ$ in this region (now $V = ω$). Comparing our prediction with experimental data, we determine one of the coupling constants in the heavy vector meson chiral Lagrangian.

hep-ph↗

arXiv1995

Hyperon Masses in Nuclear Matter

We analyze hyperon and nucleon mass shifts in nuclear matter using chiral perturbation theory. Expressions for the mass shifts that include strong interaction effects at leading order in the density are derived. Corrections to our results are suppressed by powers of the Fermi momentum divided by either the chiral symmetry breaking scale or the nucleon mass. Our work is relevant for neutron stars and for large hypernuclei.

hep-ph↗

arXiv1995

Chiral Perturbation Theory for Vector Mesons

The interactions of $ρ$, $K^*$, $ϕ$ and $ω$ vector-mesons with low-momentum $π$, $K$ and $η$ pseudoscalar mesons are constrained by chiral symmetry. We derive a heavy vector-meson chiral Lagrangian in which the vector mesons are treated as heavy static matter fields. The unknown couplings of the chiral Lagrangian are further related using the $1/N_c$ expansion. Chiral perturbation theory is applied to the vector-meson mass matrix. At one-loop there are large corrections to the individual vector meson masses, but the singlet-octet mixing angle remains almost unchanged. The parity-violating $s$-wave $\phiC \rightarrow ρπ$ weak decay amplitude is derived in the combined chiral and large $N_c$ limits. Rare $ϕ$ decays provide a sensitive test of non-leptonic neutral current structure.

hep-ph↗

arXiv1995

Final State Interactions and CP Violation in $K_L \to π^+ π^- e^+ e^-$

Using chiral perturbation theory we calculate the imaginary parts of the $K_L \rightarrow π^+ π^- e^+ e^-$ form factors that arise from $ππ\rightarrow π^+ π^-$ and $ππ\rightarrow π^+ π^- γ^*$ rescattering. We discuss their influence on CP violating variables in $K_L \rightarrow π^+ π^- e^+ e^-$.

hep-ph↗

arXiv1995

K_L to π^+ π^- e^+ e^-

We calculate all of the form factors for the one-photon, $K_L \rightarrow π^+ π^- γ^* \rightarrow π^+ π^- e^+e^-$ contribution to the $K_L \rightarrow π^+ π^- e^+e^-$ decay amplitude at leading order in chiral perturbation theory. These form factors depend on one unknown constant that is a linear combination of coefficients of local ${\cal O}(p^4)$ operators in the chiral lagrangian for weak radiative kaon decay. We determine the differential rate for $\K$ and also the magnitude of two CP violating observables.

hep-ph↗

arXiv1994

Spin symmetry predictions for heavy quarkonia alignment

We investigate the implications of spin symmetry for heavy quarkonia production and decay. We first compare spin symmetry predictions for charmonia and bottomonia radiative transitions with data and find they agree quite well. We next use spin symmetry along with nonrelativistic QCD power counting to determine the leading order alignment of P and D-wave orthoquarkonia that are produced through gluon fragmentation. Finally, we discuss a mechanism which may resolve the current factor of 30 discrepancy between theoretical predictions and experimental measurements of prompt $ψ'$ production at the Tevatron. This mechanism involves gluon fragmentation to a subleading Fock component in the $ψ'$ wavefunction and yields 100\% transversely aligned $ψ'$'s to lowest order. Observation of such a large alignment would provide strong support for this resolution to the $ψ'$ problem.

hep-ph↗

arXiv1994

Heavy Quark Theory

Recent progress in the theory of hadrons containing a single heavy quark is reviewed. Particular attention is paid to those aspects that bear on the determination of the magnitudes of the Cabibbo--Kobayashi--Maskawa matrix elements $V_{cb}$ and $V_{ub}$.}

hep-ph↗

arXiv1994

Charm Mass Dependence of the $\CO(α_s^2 n_f)$ Correction to Inclusive $B\rightarrow X_c e\barν_e$ Decay

We compute the $α_s^2 n_f$ perturbative QCD contribution to semileptonic B decay, including the finite mass of the charm quark. This result provides an estimate of the size of the two-loop correction, which is found to be about 50\% of the one-loop correction. We use these results to set the scale for the one-loop correction using the scheme of Brodsky, Lepage and Mackenzie and find a BLM scale of $μ_{\rm BLM} = 0.13\, m_b$, when the inclusive semileptonic rate is expressed in terms of the $b$ and $c$ quark pole masses and the \msbar strong coupling. The two loop correction lies roughly midway between that obtained at $m_c=0$ and that obtained in the Shifman-Voloshin limit $m_b, m_c\gg m_b-m_c\ggΛ_{\rm QCD}$ while the corresponding BLM scale is somewhat closer to that obtained in the former case.

hep-ph↗

arXiv1994

Perturbative Strong Interaction Corrections to the Heavy Quark Semileptonic Decay Rate

We calculate the part of the order $α_s^2$ correction to the semileptonic heavy quark decay rate proportional to the number of light quark flavors, and use our result to set the scale for evaluating the strong coupling in the order $α_s$ term according to the scheme of Brodsky, Lepage and Mackenzie. Expressing the decay rate in terms of the heavy quark pole mass $m_Q$, we find the scale for the $\overline{MS}$ strong coupling to be $0.07\, m_Q$. If the decay rate is expressed in terms of the $\overline{MS}$ heavy quark mass $\overline m_Q(m_Q)$ then the scale is $0.12\, m_Q$. We use these results along with the existing calculations for hadronic $τ$ decay to calculate the BLM scale for the nonleptonic decay width and the semileptonic branching ratio. The implications for the value of $|V_{bc}|$ extracted from the inclusive semileptonic $B$ meson decay rate are discussed.

hep-ph↗

arXiv1994

Strong $Λπ$ Phase Shifts for CP Violation in Weak $Ξ\rightarrow Λπ$ Decay

Strong interaction $Λπ$ phase shifts relevant for the weak nonleptonic decay $Ξ\rightarrow Λπ$ are calculated using baryon chiral perturbation theory. We find in leading order that the S-wave phase shift vanishes and the $J={1 \over 2}$ P-wave phase shift is $-1.7 ^{\rm o} $. The small phase shifts imply that CP violation in this decay will be difficult to observe. Our results follow from chiral $SU(2)_L\times SU(2)_R$ symmetry.

hep-ph↗

arXiv1994

Power Suppressed Corrections to Hadronic Event Shape Variables

For high energy processes ($M\gg Λ_{QCD}$) there are infrared safe hadronic shape variables that have a calculable perturbative expansion in $α_s(M^2)$. However, nonperturbative power suppressed corrections to these variables are not well understood. We use the behavior of large orders of the perturbation expansion to gain insight into the nonperturbative corrections. Our results suggest that certain shape variables have nonperturbative corrections suppressed by fractional powers of $Λ_{QCD}^2/M^2$.

hep-ph↗

arXiv1994

Inconclusive Inclusive Nonleptonic $B$ Decays

We reconsider the conflict between recent calculations of the semileptonic branching ratio of the $B$ meson and the experimentally measured rate. Such calculations depend crucially on the application of ``local duality'' in nonleptonic decays, and we discuss the relation of this assumption to the weaker assumptions required to compute the semileptonic decay rate. We suggest that the discrepancy between theory and experiment might be due to the channel with two charm quarks in the final state, either because of a small value for $m_c$ or because of a failure of local duality. We examine the experimental consequences of such solutions for the charm multiplicity in $B$ decays.

hep-ph↗

arXiv1994

Another Source of Baryons in $B$ Meson Decays

It is usually assumed that the production of baryons in $B$ meson decays is induced primarily by the quark level process $b\to c\bar ud$, where the charm quark hadronizes into a charmed baryon. With this assumption, the $Λ_c$ momentum spectrum would indicate that the transition $B\toΛ_c X$ is dominated by multi-body $B$ decays. However, a closer examination of the momentum spectrum reveals that the mass $m_X$ against which the $Λ_c$ is recoiling almost always satisfies $m_X\agt m_{Ξ_c}$. This fact leads us to examine the hypothesis that the production of charmed baryons in $B$ decays is in fact dominated by the underlying transition $b\to c\bar cs$, and is seen primarily in modes with two charmed baryons in the final state. We propose a number of tests of this hypothesis. If this mechanism is indeed important in baryon production, then there are interesting consequences and applications, including potentially important implications for the ``charm deficit'' in $B$ decays.

hep-ph↗

arXiv1994

Remark on Charm Quark Fragmentation to $D^{**}$ Mesons

The observed $D^{**}$ mesons have $c\bar q$ flavor quantum numbers and spin-parity of the light degrees of freedom $s_\ell^{π_{\ell}} = 3/2^+$. In the $m_c \rightarrow \infty$ limit the spin of the charm quark is conserved and the $c \rightarrow D^{**}$ fragmentation process is characterized by the probability for the charm quark to fragment to a $D^{**}$ meson with a given helicity for the light degrees of freedom. We consider the calculated $b \rightarrow B_c^{**}$ fragmentation functions in the limit $m_c/m_b \rightarrow 0$ as a qualitative model for the $c \rightarrow D^{**}$ fragmentation functions. We find that in this model charm quark fragmentation to $s_\ell^{π_{\ell}} = 3/2^+$ light degrees of freedom with helicities $\pm 1/2$ is favored over fragmentation to $s_\ell^{π_{\ell}} = 3/2^+$ light degrees of freedom with helicities $\pm 3/2$.

hep-ph↗

arXiv1994

Excited $Λ_Q$ Baryons in the Large $N_c$ Limit

The spectrum of excited $Λ_Q$-type heavy baryons is considered in the large $N_c$ limit. The universal form factors for $Λ_b$ semileptonic decay to excited charmed baryons are calculated in the large $N_c$ limit. We find that the Bjorken sum rule (for the slope of the Isgur--Wise function) and Voloshin sum rule (for the mass of the light degrees of freedom) are saturated by the first doublet of excited $Λ_Q$ states.

hep-ph↗

arXiv1994

QCD Corrections and the Endpoint of the Lepton Spectrum in Semileptonic B Decays

Recently, Neubert has suggested that a certain class of nonperturbative corrections dominates the shape of the electron spectrum in the endpoint region of semileptonic $B$ decay. Perturbative QCD corrections are important in the endpoint region. We study the effects of these corrections on Neubert's proposal. The connection between the endpoint of the electron spectrum in semileptonic $B$ decay and the photon spectrum in $b\rightarrow sγ$ is outlined.

hep-ph↗

arXiv1994

Comment on $D_s^* \to D_s π^0$ Decay

We calculate the rate for $D_s^* \rightarrow D_s π^0$ decay using Chiral Perturbation Theory. This isospin violating process results from $π^0$ - $η$ mixing, and its amplitude is proportional to $(m_d - m_u)/\bigl(m_s-(m_u+m_d)/2 \bigr)$. Experimental information on the branching ratio for $D_s^* \rightarrow D_s π^0$ can provide insight into the pattern of $SU(3)$ violation in radiative $D^*$ decays.

hep-ph↗

arXiv1994

Long Distance Contribution to $K^+ \rightarrow π^+ ν\barν$

We estimate the long distance contribution to the $K^+ \rightarrow π^+ ν\barν$ decay amplitude using chiral perturbation theory. We find that it is likely to be less than a few percent of the part of the short distance contribution proportional to the square of the charm quark mass. In the large $N_c$ limit the leading (in chiral perturbation theory) long distance contribution to $K^+ \rightarrow π^+ ν\barν$ from Feynman diagrams with a $W$ and $Z^0$ vanishes.

hep-ph↗