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Experimental cross sections for the $^4He(e,e'p)X$ reaction up to a missing momentum of 0.632 GeV/$c$ at $x_B=1.24$ and $Q^2$=2(GeV/$c$)$^2$ are reported. The data are compared to Relativistic Distorted Wave Impulse Approximation(RDWIA) calculations for $^4He(e,e'p)^3H$ channel. Significantly more events in the triton mass region are measured for $p_{m}$$>$0.45 GeV/$c$ than are predicted by the theoretical model, suggesting that the effects of initial-state multi-nucleon correlations are stronger than expected by the RDWIA model., Comment: Submitted to PRC

We present the leading order differential and total rates for J/\psi production at LEP. By leading order we mean all terms of the form alpha_s[alpha_s log(M_Z^2/M_{psi}^2)]^n and alpha_s^{n+1} log^l(z^2) log^m(M_Z^2/M_{psi}^2), (l+m=2n-1), in the regions z=2E_psi/M_Z ~ O(1) and z << 1, respectively. In the intermediate region we interpolate using the available data. This resummation eliminates the O[alpha_s(M_psi)/alpha_s(M_Z)]~ 2 theoretical uncertainties in previous calculations. The log(z) resummation results in a suppression of the small z region due to coherent gluon emission. Comparing the zeroth moment with the LEP data we find the value for the effective octet matrix element to be <\hat O_8^{\psi}(^3S_1)>=0.019 GeV^3. The theoretical uncertainties are substantially smaller than those from Tevatron extractions. Using this value of the octet matrix element we make a prediction for the first moment of the differential rate and find that the resummed differential decay rate is in much better agreement with preliminary data than the color singlet result or the unresummed color octet prediction., Comment: LATEX, 17 pages, 3 figures included. References to ALEPH collaboration changed

By calculating the O(\alpha_s) corrections to inclusive heavy-to-light sum rules we find model independent upper and lower bounds on form factors for B to pi and B to rho. We use the bounds to rule out model predictions. Some models violate the bounds only for certain ranges of sum rule input parameters \bar{lambda} \simeq m_B-m_b and lambda_1, or for certain choices of model parameters, while others obey or violate the bounds irrespective of the inputs. We discuss the reliability and convergence of the bounds, point out their utility for extracting V_{ub}, and derive from them a new form factor scaling relation., Comment: 15 pages, 3 figures included

We present precision corrections to dispersion relation bounds on form factors in bottom hadron semileptonic decays and analyze their effects on parameterizations derived from these bounds. We incorporate QCD two-loop and nonperturbative corrections to the two-point correlator, consider form factors whose contribution to decay rates is suppressed by lepton mass, and implement more realistic estimates of truncation errors associated with the parameterizations. We include higher resonances in the hadronic sum that, together with heavy quark symmetry relations near zero recoil, further tighten the sum rule bounds. Utilizing all these improvements, we show that each of the six form factors in B --> D l nu and B --> D^* l nu can be described with 3% or smaller precision using only the overall normalization and one unknown parameter. A similar one-coefficient parameterization of one of the Lambda_b --> Lambda_c l nu form factors, together with heavy quark symmetry relations valid to order 1/m^2, describes the differential baryon decay rate in terms of one unknown parameter and the phenomenologically interesting quantity (\bar Lambda)_Lambda \approx M_{Lambda_b} - m_b. We discuss the validity of slope-curvature relations derived by Caprini and Neubert, and present weaker, corrected relations. Finally, we present sample fits of current experimental B --> D^*l nu and B --> D l nu data to the improved one-parameter expansion., Comment: 45 pages, RevTeX. Version to appear in Phys. Rev. D. Improved statistical analysis reveals that our fit is competitive with ad hoc parameterizations

We give a pedagogical discussion of the physics underlying dispersion relation-derived parameterizations of form factors describing B -> pi l nu and B -> D l nu. Moments of the dispersion relations are shown to provide substantially tighter constraints on the f_+ (t) form factor describing B -> pi l nu than the unweighted dispersion relation alone. Heavy quark spin symmetry relations between the B -> pi l nu and B^* -> pi l nu form factors enables such constraints to be tightened even further., Comment: 18 pages, Latex, three eps figures included

We discuss the SU(3) and heavy quark spin-symmetry breaking mixing between the Xi_c and Xi'_c charmed baryons. Chromomagnetic hyperfine interactions are the leading source of spin-symmetry breaking and together with the SU(3) breaking mass differences between the lightest pseudo-Goldstone bosons gives the leading contribution to the mixing. Such contributions are computed in chiral perturbation theory and compared to quark model expectations. We also compute the leading contribution to the semileptonic decay Xi_b -> Xi'_c l nu at zero recoil, and find that it is an order of magnitude smaller than naive power counting would suggest. It appears that Xi_b -> Xi'_c l nu is dominated by incalculable counterterms, and we discuss the implications for quark models based on the essential role of hyperfine interactions., Comment: 10 pages, LaTex, uses revtex, two eps figures

We calculate near zero recoil the order $\alpha_s$ corrections to the Bjorken and Voloshin sum rules that bound the $B\to D^{(*)}\ell\bar\nu$ 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 $\Delta$. We find that the corrections to the Bjorken bound are moderate, while the Voloshin bound receives sizable corrections enhanced by $\Delta/\Lambda_{QCD}$. With some assumptions, we find that the slope parameter for the form factor $h_{A_1}$ in $B\to D^*\ell\bar\nu$ decay satisfies $0.4\lesssim\rho_{A_1}^2 \lesssim 1.3$., Comment: 26 pages, revtex, 5 figures included using epsf. Some references added; to appear in Phys. Rev. D

We utilize inclusive sum rules to construct both upper and lower bounds on the form factors for B to D, D*, rho, pi, omega, K and K* semi-leptonic and radiative decays. We include the leading nonperturbative 1/E corrections and point out cases when alpha_s corrections are equally important. We compute the alpha_s correction to the lower bound on the B to D* form factor f(w) at zero recoil, thereby constraining its normalization f(1) to within 6-8% of the upper bound. We show that the B to rho form factor a_+ is suppressed at small momentum transfer by either a factor of 1/E or alpha_s. These bounds can be used to rule out phenomenological models as well as to determine values for the CKM matrix elements once radiative corrections are included., Comment: LATEX file, 16 pages, 3 figures included

We construct model-independent parametrizations of the individual QCD form factors relevant to Lambda_b --> Lambda_c l nu decays. These results follow from dispersion relations and analyticity, and incorporate an improvement in the technique that reduces the number of necessary parameters. To describe most form factors with 5%--10% accuracy over the entire kinematic range, three parameters are necessary, one of which is its normalization at zero recoil. We also apply the improvement to meson decays, and find, using the heavy quark form factor normalization, that almost every B --> D l nu and B --> D^* l nu form factor is well-described by a single-variable parametrization. B --> pi l nu requires a total of only 3 to 5 parameters, depending on the desired accuracy., Comment: 19 pages, 2 figures, one in eps, one in ps; uses epsf.tex and lanlmac.tex (harvmac.tex). Version accepted by Nuc. Phys. B. Includes a more detailed discussion of branch cuts and minor modifications to wording and numerical results

The inclusive and exclusive semileptonic decay distributions for b -> c decay are computed in the Shifman-Voloshin limit. The inclusive decay distributions (computed using an operator product expansion) depend on quark masses, and the exclusive decay distributions depend on hadron masses. Nevertheless, we show explicitly how the first two terms in the 1/m expansion match between the inclusive and exclusive decays. Agreement between the inclusive and exclusive decay rates requires a minimum smearing region of size Lambda_QCD before local duality holds in QCD. The alpha_s corrections to the inclusive and exclusive decay rates are also shown to agree to order (log m)/m^2. The alpha_s/m^2 corrections are used to obtain the alpha_s correction to Bjorken's inequality on the slope of the Isgur-Wise function., Comment: 22 pages, 3 eps figures, uses revtex (Revision: a discussion of radiative corrections to the bound K>0 of Section 7.B has been added; some typos, including labels in fig 2)

We present a method for parametrizing heavy meson semileptonic form factors using dispersion relations, and from it produce a two-parameter description of the B -> B elastic form factor. We use heavy quark symmetry to relate this function to B -> D* l nu form factors, and extract |V_cb|=0.0355^{+0.0029}_{-0.0025} from experimental data with a least squares fit. Our method eliminates model-dependent uncertainties inherent in choosing a parametrization for the extrapolation of the differential decay rate to threshold., Comment: uses lanlmac(harvmac) and epsf, 12 pages, 1 eps figure included (Talk by BG at the 6-th International Symposium on Heavy Flavour Physics, Pisa, Italy, 6--10 June, 1995)

We present nonperturbative, model-independent parametrizations of the individual QCD form factors relevant to B -> D* l nu and B -> D l nu decays. These results follow from dispersion relations and analyticity, without recourse to heavy quark symmetry. To describe a form factor with two percent accuracy, three parameters are necessary, one of which is its normalization at zero recoil, F(1). We combine the individual form factors using heavy quark symmetry to extract values for the product |V_{cb}| F(1) from B -> D* l nu data with negligible extrapolation uncertainty., Comment: uses harvmac and epsf, 22 pages, 3 eps figures included

We present a method for parametrizing heavy meson semileptonic form factors using dispersion relations, and from it produce a two-parameter description of the B -> B elastic form factor. We use heavy quark symmetry to relate this function to B->D* l \nu form factors, and extract |V_{cb}|=0.037^{+0.003}_{-0.002} from experimental data with a least squares fit. Our method eliminates model-dependent uncertainties inherent in choosing a parametrization for the extrapolation of the differential decay rate to threshold. The method also allows a description of B -> D l nu form factors accurate to 1% in terms of two parameters., Comment: 12 pages, 2 eps figures, uuencoded. Uses epsf.

We compute the O(1/M,m_s) heavy quark and SU(3) corrections to B_s -> D_s e nu form factors. In the limit of vanishing light quark mass, B_s -> D_s e nu form factors are given in terms of the the B -> D e nu form factors, the leading order chiral parameter g, and two O(1/M) chiral parameters $g_1$ and $g_2$. All the chiral parameters can be extracted, in principle, from other heavy meson decays. Analytic counterterms proportional to the strange quark mass are presented for completeness, but no predictive power remains when they are included. Anomalously large loop corrections warn of poor convergence of the heavy quark chiral symmetry expansion for these processes. This suggests that naive extrapolations of B \to D form factors relying on heavy quark and chiral symmetries, as often used in monte carlo simulations of lattice QCD, may incur large errors., Comment: uuencoded, 24 pages, 6 eps figures, uses lanlmac/harvmac (suggest `b' size) and epsf.tex (if you want auto-insertion of figs).

We use rigorous QCD dispersion relations to derive model-independent bounds on the B -> pi l nu, D -> pi l nu and D -> K l nu form factors. These bounds are particularly restrictive when the value of the observable form factor at one or more kinematic points is assumed. With reasonable assumptions we find f_B < 195 MeV and that the shape of the form factor becomes severely constrained. These constraints are useful both for model discrimination and for model-insensitive extraction of CKM mixing parameters., Comment: Fixed for auto-ps generator. 8 pages, 2 figures, uses epsf.tex and lanlmac.tex. (Shortened to comply with Phys. Rev. Lett editorial standards. Higher quality figures.)

We calculate the $\alpha_s$ corrections to the form factors which parameterize the hadronic tensor relevant for inclusive semileptonic $B \rightarrow X \tau\bar\nu_{\tau}$ and $\Lambda_b \rightarrow X \tau\bar\nu_{\tau}$ decays. We apply our results to the double differential decay rates for the decays of $B$ mesons and polarized $\Lambda_b$ baryons to polarized $\tau$ leptons, presenting them in terms of one-dimensional integrals. Formulas appropriate for insertion into a Monte-Carlo simulation are presented., Comment: 30 pages, TeX using harvmac and epsf, figures tarred and gzipped in separate file

The most general Lagrangian consistent with chiral, heavy quark, and strong interaction symmetries to order $1/M$ and to linear order in the SU(3) vector and axial currents is presented. Two new dimensionful and five dimensionless couplings arise at this order. The heavy to light flavor changing current is derived to the same order, giving rise to two additional dimensionful constants and six dimensionless ones. The dimensionless parameters are shown to be irrelevant at \ord. The leading nonanalytic heavy quark and chiral symmetry violating corrections to heavy meson decay constants are computed, and implications to B decays are discussed; measurements of the experimentally accessible form factors for $D \to \pi l \nu$ and $B \to \pi l \nu$, along with knowledge of the $D^* D \pi$ coupling, determine the eight decay constants $f_D$, $f_{D_s}$, $f_{D^*}$, $f_{D_s^*}$, $f_B$, $ f_{B_s}$, $f_{B^*}$, and $f_{B_s^*}$, as well as one relation among the $B \to \pi l \nu$ form factors, to \ord~. The ratio $R_1 = \frac{f_{B_s}}{f_B}/\frac{f_{D_s}}{f_D}$ is expressed in terms of two dimensionful couplings., Comment: 22 pages, harvmac, 5 eps figs, resubmitted for automated postscript

We examine several resummation methods for computing higher order corrections to the finite temperature effective potential, in the context of a scalar $\phi^4$ theory. We show by explicit calculation to four loops that dressing the propagator, not the vertex, of the one-loop tadpole correctly counts ``daisy'' and ``super-daisy'' diagrams., Comment: 18 pages, LaTeX, CALT-68-1858, HUTP-93-A011, EFI-93-22

The implications of chiral $SU(3)_L \times SU(3)_R$ symmetry and heavy quark symmetry for the radiative decays $D^{*0}\to D^0\gamma$, $D^{*+}\to D^+\gamma$, and $D_s^*\to D_s\gamma$ are discussed. Particular attention is paid to $SU(3)$ violating contributions of order $m_q^{1/2}$. Experimental data on these radiative decays provide constraints on the $D^* D\pi$ coupling., Comment: 9 pages plus 3 pages of figures in POSTSCRIPT file appended to TeX file (uses harvmac.tex and tables.tex), UCSD/PTH 92-31, CALT-68-1816, EFI-92-45, CERN-TH.6650/92

We calculate contributions to the finite temperature effective action for the electroweak phase transition (EWPT) at $\O(g^4)$, {\it i.e.} at second order in $(g^2 T/\M)$ and all orders in $(g^2 T^2/\M^2)$. This requires plasma-mass corrections in the calculation of the effective potential, inclusion of the ``lollipop'' diagram, and an estimate of derivative corrections. We find the EWPT remains too weakly first-order to drive baryogenesis. We calculate some one loop kinetic energy corrections using both functional and diagrammatic methods; these may be important for saddlepoint configurations such as the bounce or sphaleron., Comment: LaTeX, 6 figures available by email, CALT-68-1795, HUTP-92-A027, EFI-92-22