Within the framework of transverse-momentum-dependent factorization, we investigate for the first time the impact of a flavor-dependent intrinsic transverse momentum of quarks on the production of $W^{pm}$ bosons in proton-proton collisions at $sqrt{s}$ = 7 TeV. We estimate the shift in the extracted value of the $W$ boson mass $M_W$ induced by different choices of flavor-dependent parameters for the intrinsic quark transverse momentum by means of a template fit to the transverse-mass and the lepton transverse-momentum distributions of the $W$-decay products. We obtain $-6leq Delta M_{W^+} leq 9$ MeV and $-4leq Delta M_{W^-} leq 3$ MeV with a statistical uncertainty of $pm 2.5$ MeV. Our findings call for more detailed investigations of flavor-dependent nonperturbative effects linked to the proton structure at hadron colliders.
The energy and rapidity dependence of the average transverse momentum $langle p_T rangle$ in $pp$ and $pA$ collisions at RHIC and LHC energies are estimated using the Colour Glass Condensate (CGC) formalism. We update previous predictions for the $p_T$ - spectra using the hybrid formalism of the CGC approach and two phenomenological models for the dipole - target scattering amplitude. We demonstrate that these models are able to describe the RHIC and LHC data for the hadron production in $pp$, $dAu$ and $pPb$ collisions at $p_T le 20$ GeV. Moreover, we present our predictions for $langle p_T rangle$ and demonstrate that the ratio $langle p_{T}(y)rangle / langle p_{T}(y = 0)rangle$ decreases with the rapidity and has a behaviour similar to that predicted by hydrodynamical calculations.
We demonstrate that spontaneous transverse polarization of Lambda baryon ($Lambda$) production in $e^+e^-$ annihilation can be described using the transverse momentum dependent polarizing fragmentation functions (TMD PFFs). Using a simple Gaussian model, we perform an extraction of the TMD PFFs by fitting the BELLE collaborations recent measurement of the $Lambda$ transverse polarization in back-to-back $Lambda+h$ production in $e^+ e^-$ collisions, $e^{-} + e^{+} rightarrow Lambda^{uparrow}+h+X$. We find that this simple model accurately describes the experimental data for $Lambda$ production associated with pions and kaons, and we are able to determine TMD PFFs for different quark flavors. We use these newly extracted TMD PFFs to make predictions for the transverse polarization of $Lambda$ produced in semi-inclusive deep inelastic scattering at a future electron-ion collider, and find that such a polarization is around $10%$ and should be measurable.
Previous studies of the physics potential of LEP2 indicated that with the design luminosity of 500 inverse picobarn one may get a direct measurement of the mass of the W-boson with a precision in the range 30 - 50 MeV. This report presents an updated evaluation of the estimated error on the mass of the W-boson based on recent simulation work and improved theoretical input. The most efficient experimental methods which will be used are also described.
We calculate the full one-loop electroweak radiative corrections to the cross section of single W-boson inclusive hadroproduction at finite transverse momentum (p_T). This includes the O(alpha) corrections to W+j production, the O(alpha_s) corrections to W+gamma production, and the tree-level contribution from W+j photoproduction with one direct or resolved photon in the initial state. We present the integrated cross section as a function of a minimum-p_T cut as well as the p_T distribution for the experimental conditions at the Fermilab Tevatron and the CERN LHC and estimate the theoretical uncertainties.
We investigate the predictive power of transverse-momentum-dependent (TMD) distributions as a function of the light-cone momentum fraction $x$ and the hard scale $Q$ defined by the process. We apply the saddle point approximation to the unpolarized quark and gluon transverse momentum distributions and evaluate the position of the saddle point as a function of the kinematics. We determine quantitatively that the predictive power for an unpolarized transverse momentum distribution is maximal in the large-$Q$ and small-$x$ region. For cross sections the predictive power of the TMD factorization formalism is generally enhanced by considering the convolution of two distributions, and we explicitly consider the case of $Z$ and $H^0$ boson production. In the kinematic regions where the predictive power is not maximal, the distributions are sensitive to the non-perturbative hadron structure. Thus, these regions are critical for investigating hadron tomography in a three-dimensional momentum space.
Alessandro Bacchetta
,Giuseppe Bozzi
,Marco Radici
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(2018)
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"Effect of flavor-dependent partonic transverse momentum on the determination of the $W$ boson mass in hadronic collisions"
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Marco Radici
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