508 research outputs found
The Polarized Two-Loop Massive Pure Singlet Wilson Coefficient for Deep-Inelastic Scattering
We calculate the polarized massive two--loop pure singlet Wilson coefficient
contributing to the structure functions analytically in the whole
kinematic region. The Wilson coefficient contains Kummer--elliptic integrals.
We derive the representation in the asymptotic region , retaining
power corrections, and in the threshold region. The massless Wilson coefficient
is recalculated. The corresponding twist--2 corrections to the structure
function are obtained by the Wandzura--Wilczek relation. Numerical
results are presented.Comment: 22 pages Latex, 8 Figure
calculations for the inclusive determination of
For the determination of the Cabbibo-Kobayashi-Maskawa matrix element from inclusive data precise knowledge of the semileptonic decay rate is necessary. Since this observable has a bad convergence behavior when the heavy quark masses are expressed in the on-shell or scheme the latest determinations have been obtained in the so called kinetic mass scheme. The relation between the different schemes needs to be known to high precision as well. In this proceedings we present our recent calculations which push the precision of both ingredients to ). The results can be used to improve the inclusive determination of
Massive form factors at O(a)
We report on our recent calculation of massive quark form factors using a semi-numerical approach based on series expansions of the master integrals around singular and regular kinematic points and numerical matching. The methods allows to cover the whole kinematic range of negative and positive values of the virtuality with at least seven significant digits accuracy
Double hard scattering without double counting
Double parton scattering in proton-proton collisions includes kinematic
regions in which two partons inside a proton originate from the perturbative
splitting of a single parton. This leads to a double counting problem between
single and double hard scattering. We present a solution to this problem, which
allows for the definition of double parton distributions as operator matrix
elements in a proton, and which can be used at higher orders in perturbation
theory. We show how the evaluation of double hard scattering in this framework
can provide a rough estimate for the size of the higher-order contributions to
single hard scattering that are affected by double counting. In a numeric
study, we identify situations in which these higher-order contributions must be
explicitly calculated and included if one wants to attain an accuracy at which
double hard scattering becomes relevant, and other situations where such
contributions may be neglected.Comment: 80 pages, 20 figures. v2: clarifications in section 4, extended
section 8, small changes elsewher
Subleading Logarithmic QED Initial State Corrections to to
Using the method of massive operator matrix elements, we calculate the
subleading QED initial state radiative corrections to the process for the first three logarithmic contributions from
to and compare their effects to the leading
contribution and one more subleading term .
The calculation is performed in the limit of large center of mass energies
squared . These terms supplement the known corrections to
, which were completed recently. Given the high precision at
future colliders operating at very large luminosity, these corrections are
important for concise theoretical predictions. The present calculation needs
the calculation of one more two--loop massive operator matrix element in QED.
The radiators are obtained as solutions of the associated Callen--Symanzik
equations in the massive case. The radiators can be expressed in terms of
harmonic polylogarithms to weight {\sf w = 6} of argument and and
in Mellin space by generalized harmonic sums. Numerical results are
presented on the position of the peak and corrections to the width,
. The corrections calculated result into a final theoretical accuracy
for and which is estimated to be of O(30 keV) at
an anticipated systematic accuracy at the FCC\_ee of \sim 100 keV. This
precision cannot be reached, however, by including only the corrections up to
.Comment: 58 pages, 3 Figure
Massive form factors at
We report on our recent calculation of massive quark form factors using a
semi-numerical approach based on series expansions of the master integrals
around singular and regular kinematic points and numerical matching. The
methods allows to cover the whole kinematic range of negative and positive
values of the virtuality with at least seven significant digits accuracy.Comment: 9 pages, 3 figures, contribution to the proceedings of Loops and Legs
in Quantum Field Theory (LL2022), Ettal, German
Forfeiture of Attorney\u27s Fees Under RICO and CCE
We present the matching relations of the variable flavor number scheme at next-to-leading order, which are of importance to define heavy quark partonic distributions for the use at high energy colliders such as Tevatron and the LHC. The consideration of the two-mass effects due to both charm and bottom quarks, having rather similar masses, are important. These effects have not been considered in previous investigations. Numerical results are presented for a wide range of scales. We also present the corresponding contributions to the structure function
Massive form factors at O(a)
We report on our recent calculation of massive quark form factors using a semi-numerical approach based on series expansions of the master integrals around singular and regular kinematic points and numerical matching. The methods allows to cover the whole kinematic range of negative and positive values of the virtuality with at least seven significant digits accuracy
calculations for the inclusive determination of
For the determination of the Cabbibo-Kobayashi-Maskawa matrix element |Vcb| from inclusive data precise knowledge of the semileptonic b→c decay rate is necessary. Since this observable has a bad convergence behavior when the heavy quark masses are expressed in the on-shell or MS¯¯¯¯¯¯¯ scheme the latest determinations have been obtained in the so called kinetic mass scheme. The relation between the different schemes needs to be known to high precision as well. In this proceedings we present our recent calculations which push the precision of both ingredients to O(α3s). The results can be used to improve the inclusive determination of |Vcb|
Phase-matched few-cycle high-harmonic generation: ionisation gating and half-cycle cutoffs
For the direct exploration of electron dynamics in molecules, e.g. during a chemical reaction, a short pulsed radiation source is required, delivering flashes of duration less than a femtosecond. Due to their wavelengths conventional laser pulses cannot be shortened enough to reach such pulse durations. High-harmonic generation (HHG) is currently the key to the subfemtosecond regime with wavelengths in the extreme-ultraviolet and soft-X-ray range. HHG is a very inefficient process and, therefore, the radiation produced by every atom involved has to be phase-matched to obtain a macroscopic signal. The intrinsic characteristics of phase matching provide the possibility to produce even single attosecond pulses. A simulation will show, how phase matching acts as temporal gate and allows HHG only at the leading-edge of the driving laser pulse. The behaviour of the leading-edge gating will be analysed for different experimental conditions, such as peak intensity of the laser pulse, density of the gaseous generation medium and the distance between focus and generation region. Half-cycle cutoff (HCO) analysis allows an experimental access to observing the leading-edge gate, that will be compared to the simulation. The HCO-analysis can also be used to estimate the duration of the driving laser pulse. In addition the position- and pressure dependence of the HHG process will be analysed, too
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