56195115
Doubly Heavy Baryons, Heavy Quark-DiQuark Symmetry and NRQCD
In the heavy quark limit, properties of heavy mesons and doubly heavy baryons are related by heavy quark-diquark symmetry. This problem is reanalyzed in the framework of Non-Relativistic QCD (NRQCD). We introduce a novel method for deriving Potential NRQCD (pNRQCD) Lagrangians for composite fields from vNRQCD, which contains quarks and antiquarks as explicit degrees of freedom and maintains manifest power counting in the velocity via a label formalism. A Hubbard-Stratonovich transformation is used to eliminate four quark interactions in vNRQCD and then quarks and antiquarks are integrated out to get effective Lagrangians for composite fields. This method is used to rederive Lagrangians for the Q ¯
15369742
J/Ψ photo-production at large z in soft collinear effective theory
One of the outstanding problems in J/{psi} physics is a systematic understanding of the differential photo-production cross section d{sigma}/dz({gamma} + p {yields} J/{psi} + X), where z = E{sub {psi}}/E{sub {gamma}} in the proton rest frame. The theoretical prediction based on the non-relativistic QCD (NRQCD) factorization formalism has a color-octet contribution which grows rapidly in the endpoint region, z {yields} 1, spoiling perturbation theory. In addition there are subleading operators which are enhanced by powers of 1/(1-z) and they must be resumed to all orders. Here an update of a systematic analysis is presented. The approach used to organize the endpoint behavior of the photo-production cross section is based on a combination of NRQCD and soft collinear effective theory. While a final result is not yet available, an intermediate result indicates that better agreement between theory and data will be achieved in this framework.
54173137
Even- and odd-parity charmed meson masses in heavy hadron chiral perturbation theory
We derive mass formulae for the ground state, J P = 0 − and 1 − , and first excited even-parity, J P = 0 + and 1 + , charmed mesons including one loop chiral corrections and O(1/mc) counterterms in heavy hadron chiral perturbation theory. We show that including these counterterms is critical for fitting the current data. We find that certain parameter relations in the parity doubling model are not renormalized at one loop, providing a natural explanation for the observed equality of the hyperfine splittings of ground state and excited doublets.
5548289
Excited heavy mesons beyond leading order in the heavy quark expansion.
We examine the decays of excited heavy mesons, including the leading power corrections to the heavy quark limit. We find a anew and natural explanation for the large deviation of the width of the {ital D}{sub 1}(2420) from the heavy quark symmetry prediction. Our formalism leads to detailed predictions for the properties of the excited bottom mesons, some of which recently have been observed. Finally, we present a detailed analysis of the effect of power corrections and finite meson widths on the angular distributions which may be measured in heavy meson decays. {copyright} {ital 1995 The American Physical Society.}
27024410
On the equivalence of soft and zero-bin subtractions
Zero-bin subtractions are required to avoid double counting soft contributions in collinear loop integrals in soft-collinear effective theory (SCET). In traditional approaches to factorization, double counting is avoided by dividing jet functions by matrix elements of soft Wilson lines. In this paper, we compare the two approaches to double counting, studying the quark form factor and deep inelastic scattering (DIS) as ${x}_{B}\ensuremath{\rightarrow}1$ as examples. We explain how the zero-bin subtractions in SCET are required to reproduce the well-established factorization theorem for DIS as ${x}_{B}\ensuremath{\rightarrow}1$. We study one-loop virtual contributions to the quark form factor and real gluon emission diagrams in DIS. The two approaches to double counting are equivalent if dimensional regularization (DR) is used to regulate infrared (IR) divergences. We discuss in detail ambiguities in the calculation of one-loop scaleless integrals in DR in SCET and perturbative QCD. We also demonstrate a nontrivial check of the equivalence of the zero-bin subtraction and the soft Wilson line subtraction in the virtual two-loop Abelian contributions to the quark form factor.
56195115
Doubly Heavy Baryons, Heavy Quark-DiQuark Symmetry and NRQCD
In the heavy quark limit, properties of heavy mesons and doubly heavy baryons are related by heavy quark-diquark symmetry. This problem is reanalyzed in the framework of Non-Relativistic QCD (NRQCD). We introduce a novel method for deriving Potential NRQCD (pNRQCD) Lagrangians for composite fields from vNRQCD, which contains quarks and antiquarks as explicit degrees of freedom and maintains manifest power counting in the velocity via a label formalism. A Hubbard-Stratonovich transformation is used to eliminate four quark interactions in vNRQCD and then quarks and antiquarks are integrated out to get effective Lagrangians for composite fields. This method is used to rederive Lagrangians for the Q ¯