118679055
NNLO soft function for electroweak boson production at large transverse momentum
A bstractThe soft function relevant for the production of an electroweak boson (γ, W, Z or H) with large transverse momentum at a hadron collider is computed at next-to-next-to-leading order. This is the first two-loop computation of a soft function describing emissions from energetic partons in three directions. With the result, the threshold resummation for these processes can now be performed at next-to-next-to-next-to-leading logarithmic accuracy.
14116539
NNLO corrections to inclusive semileptonic B decays in the shape-function region
Abstract We compute 2-loop QCD corrections to the hard coefficient functions which arise in the factorization formula for B → X u l ν decays in the shape-function region. Our calculation provides the last missing piece required for a NNLO analysis of inclusive semileptonic B decays, which may significantly reduce the theoretical uncertainty in the extraction of the CKM matrix element | V u b | . Among the technical aspects, we find that the 2-loop hard coefficient functions are free of infrared singularities as predicted by the factorization framework. We perform a brief numerical analysis of the NNLO corrections and include a discussion on charm mass effects.
56450914
NNLO corrections to semileptonic and hadronic B decays
We review recent progress in the perturbative calculations for semileptonic and hadronic B meson decays with an emphasis on the phenomenological implications of the next-to-next-to-leading order (NNLO) corrections. Specifically, we consider CP-averaged branching ratios of tree-dominated B -> pi pi/pi rho/rho rho decays and the inclusive determination of |V_ub| from B -> X_u l nu.
118509342
Master integrals for the two-loop penguin contribution in non-leptonic B-decays
A bstractWe compute the master integrals that arise in the calculation of the leading penguin amplitudes in non-leptonic B-decays at two-loop order. The application of differential equations in a canonical basis enables us to give analytic results for all master integrals in terms of iterated integrals with rational weight functions. It is the first application of this method to the case of two different internal masses.
43936826
The transverse-momentum spectrum of Higgs bosons near threshold at NNLO
A bstractWe give next-to-next-to-leading order (NNLO) predictions for the Higgs production cross section at large transverse momentum in the threshold limit. Near the partonic threshold, all radiation is either soft or collinear to the final state jet which recoils against the Higgs boson. We find that the real emission corrections are of moderate size, but that the virtual corrections are large. We discuss the origin of these corrections and give numerical predictions for the transverse-momentum spectrum. The threshold result is matched to the known NLO result and implemented in the public code PeTeR.
119143806
Higher order QCD corrections in exclusive charmless B decays
We discuss exclusive charmless B decays within the Standard Model of particle physics. In particular we compute part of the NNLO corrections for hadronic two-body decays in the framework of QCD Factorization. We also present a conceptual analysis of heavy-to-light form factors at large recoil.
124991742
COUPLING MODULATOR SIMULATIONS INTO AN FEL AMPLIFIER FOR COHERENT ELECTRON COOLING
Next-generation ion colliders will require effective cooling of high-energy hadron beams. Coherent electron cooling (CeC) can in principle cool relativistic hadron beams on orders-of-magnitude shorter time scales than other techniques [1]. Particle-in-cell (PIC) simulations of a CeC modulator with the parallel VORPAL framework generate macro-particle distributions with subtle but important phase space correlations. To couple these macro-particles into a 3D simulation code for the free-electron laser (FEL) amplifier, while retaining all details of the 6D phase space coordinates, we implemented an alternative approach based on particle-clone pairs [2]. Our approach allows for selfconsistent treatment of shot noise and spontaneous radiation, with no need for quiet-start initialization of the FEL macro-particles’ ponderomotive phase. We present results of comparing fully 3D amplifier modeling based on the particle-clone approach vs GENESIS [3] simulations where distribution of bunching parameter was used as input.
15379716
VORPAL simulations relevant to coherent electron cooling
Coherent electron cooling (CEC) [1] combines the best features of electron cooling and stochastic cooling, via free-electron laser technology [2], to offer the possibility of cooling high-energy hadron beams with order-of-magnitude shorter cooling times. Many technical difficulties must be resolved via full-scale 3D simulations, before the CEC concept can be validated experimentally. VORPAL is the ideal code for simulating the modulator and kicker regions, where the electron and hadron beams will co-propagate as in a conventional electron cooling section. Unlike previous VORPAL simulations [3] of electron cooling physics, where dynamical friction on the ions was the key metric, it is the details of the electron density wake driven by each ion in the modulator section that must be understood, followed by strong amplification in the FEL. We present some initial simulation results.
53999449
Advances in Coherent Electron Cooling
Cooling techniques are required for improving the quality of hadron beams and increasing the luminosity in hadron- and electron-hadron-colliders. In contrast to light leptons that have very strong radiation damping via synchrotron radiation, the hadrons radiate very little (even in a 7-TeV LHC) and require an additional cooling mechanism to control the growth or reduce their emittances. In this paper, we focus on the advances in, and challenges of Coherent Electron Cooling (CeC) that promises to be an effective method of cooling of high-energy hadron beams, and potentially even ultra-relativistic muon beams. Specifically, we describe the underlying physics principles, and the advances in this revolutionary, but yet untested, technique: viz., CeC. While we described physics principles in an earlier paper [1], our comprehensive studies revealed several other important factors affecting the CeC’s performance [2-5]. In this paper, we summarize our main findings as well as presenting current advances and novel CeC schemes. We also briefly describe the CeC demonstration experiment under preparation at Brookhaven National Laboratory; its detailed description is part of these proceedings [6].
119910077
FISSION AND THE SYNTHESIS OF HEAVY NUCLEI BY RAPID NEUTRON CAPTURE.
119104094
Modulator simulations for coherent electron cooling using a variable density electron beam
Increasing the luminosity of relativistic hadron beams is critical for the advancement of nuclear physics. Coherent electron cooling (CEC) promises to cool such beams significantly faster than alternative methods. We present simulations of 40 GeV/nucleon Au+79 ions through the first (modulator) section of a coherent electron cooler. In the modulator, the electron beam copropagates with the ion beam, which perturbs the electron beam density and velocity via anisotropic Debye shielding. In contrast to previous simulations, where the electron density was constant in time and space, here the electron beam has a finite transverse extent, and undergoes focusing by quadrupoles as it passes through the modulator. The peak density in the modulator increases by a factor of 3, as specified by the beam Twiss parameters. The inherently 3D particle and field dynamics is modeled with the parallel VSim framework using a $\delta$f PIC algorithm. Physical parameters are taken from the CEC proof-of-principle experiment under development at Brookhaven National Lab.