Transverse Momentum In Hadronic Collisions Research Articles

Higgs boson production at large transverse momentum within the SMEFT: analytical results

We consider Higgs boson production through gluon fusion at large transverse momentum in hadronic collisions. We present the analytic expressions of the relevant one-loop QCD amplitudes including the effects of the complete set of dimension-six operators. The latter correspond to modifications of the top and bottom Yukawa couplings, to an effective point-like Higgs coupling to gluons and to the chromomagnetic operator of the top quark. The quantitative impact of the chromomagnetic operator is also studied. Our results confirm previous findings that the effect of the chromomagnetic operator at high p_T can be large and should not be neglected.

Rapidity dependence of the average transverse momentum in hadronic collisions

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.

Top quark pair production at small transverse momentum in hadronic collisions

We investigate the transverse momentum resummation for top quark pair production at hadron colliders using the soft-collinear effective theory and the heavy-quark effective theory. We derive the factorization formula for $t\overline{t}$ production at the small pair transverse momentum, and show in detail the procedure for calculating the key ingredient of the factorization formula: the next-to-leading order soft functions. We compare our numerical results with experimental data and find that they are consistent within theoretical and experimental uncertainties. To verify the correctness of our resummation formula, we expand it to the next-to-leading order and the next-to-next-to-leading order, and compare those expressions with the exact fixed-order results numerically. Finally, using the results of transverse momentum resummation, we discuss the transverse-momentum-dependent forward-backward asymmetry at the Tevatron.

Heavy quarkonium production at lowP⊥in nonrelativistic QCD with soft gluon resummation

We extend the non-relativistic QCD (NRQCD) prediction for the production of heavy quarkonium with low transverse momentum in hadronic collisions by taking into account effects from all order soft gluon resummation. Following the Collins-Soper-Sterman formalism, we resum the most singular terms in the partonic subprocesses. The theoretical predictions of $J/\psi$ and $\Upsilon$ productions are compared to the experimental data from the fixed target experiments (E866) and the collider experiments (RHIC, Tevatron, LHC). The associated non-perturbative Sudakov form factor for the gluon distributions is found to be different from the previous assumption of rescaling the quark form factor by the ratio of color factors. This conclusion should be further checked by future experiments on Higgs boson and/or di-photon production in $pp$ collisions. We also comment on the implication of our results on determining the color-octet matrix elements associated with the $J/\psi$ and $\Upsilon$ productions in the NRQCD factorization formalism.

Soft-gluon resummation for single-particle inclusive hadroproduction at high transverse momentum

We consider the cross section for one-particle inclusive production at high transverse momentum in hadronic collisions. We present the all-order resummation formula that controls the logarithmically-enhanced perturbative QCD contributions to the partonic cross section in the threshold region, at fixed rapidity of the observed parton (hadron). The explicit resummation up to next-to-leading logarithmic accuracy is supplemented with the computation of the general structure of the near-threshold contributions to the next-to-leading order cross section. This next-to-leading order computation allows us to extract the one-loop hard-virtual amplitude that enters into the resummation formula. This is a necessary ingredient to explicitly extend the soft-gluon resummation beyond the next-to-leading logarithmic accuracy. These results equally apply to both spin-unpolarized and spin-polarized scattering processes.

The structure of large logarithmic corrections at small transverse momentum in hadronic collisions

We consider the region of small transverse momenta in the production of high-mass systems in hadronic collisions. By using the current knowledge on the infrared behaviour of tree-level and one-loop QCD amplitudes at O(α S 2) , we analytically compute the general form of the logarithmically-enhanced contributions up to next-to-next-to-leading logarithmic accuracy. By comparing the results with q T -resummation formulae we extract the coefficients that control the resummation of the large logarithmic contributions for both quark and gluon channels. Our results show that within the conventional resummation formalism the Sudakov form factor is actually process-dependent.

Electroweak-boson hadroproduction at large transverse momentum: factorization, resummation, and NNLO corrections

We study the resummation of singular distributions for electroweak-boson production at large transverse momentum in hadronic collisions. We describe the factorization properties of the cross section near partonic threshold and construct the resummed cross section at next-to-leading logarithmic accuracy in moment space in terms of soft gluon anomalous dimensions. We present full analytical results for the expansion of the resummed cross section up to next-to-next-to-leading order. Our results can be applied to W, Z, and virtual γ production at hadron colliders.

Higgs Production with Large Transverse Momentum in Hadronic Collisions at Next-to-Leading Order

Inclusive associated production of a light Higgs boson with one jet in $\mathrm{pp}$ collisions is studied in next-to-leading order quantum chromodynamics. Transverse momentum and rapidity distributions of the Higgs boson are calculated for the LHC in the large top-quark mass limit. We find that the $K$-factor of this process is large $(\ensuremath{\approx}1.6)$. Our result supports previous suggestions that the production channel $p+p\ensuremath{\rightarrow}H+\mathrm{jet}$ $\ensuremath{\rightarrow}\ensuremath{\gamma}+\ensuremath{\gamma}+\mathrm{jet}$ gives a measurable signal for Higgs production at the LHC in the mass range $100--140\mathrm{GeV}$.

W and Z polarization effects in hadronic collisions.

A Monte Carlo study of the polar and azimuthal angular distributions of the lepton pair arising from the decay of a $W$ or $Z$ boson produced at high transverse momentum in hadronic collisions is presented. In the absence of cuts on the final state leptons, the lepton angular distribution in the gauge boson rest frame is determined by the gauge boson polarization. Numerical results for the lepton angular distributions in the Collins--Soper frame with acceptance cuts and energy resolution smearing applied to the leptons are presented. In the presence of cuts, the lepton angular distributions are dominated by kinematic effects rather than polarization effects, however, some polarization effects are still observable on top of the kinematic effects. Polarization effects are highlighted when the experimental distributions are divided by the Monte Carlo distributions obtained using isotropic gauge boson decay.

Probing the three-gluon coupling of QCD using heavy quark and quarkonium production in hadronic collisions

The production of heavy quarks and quarkonia at large transverse momentum in hadronic collisions depends on the non-Abelian three-gluon coupling of QCD. We examine what limits can be placed on deviations of this coupling from its gauge theory form by confrontation with experimental data on b-quark and charmonium ( J ψ ) production at large p T . We also briefly discuss the effects of a non-standard three-gluon coupling on the hadronic decay width of the 3P 1(c c) charmonium state.

Probing the polarized gluon distribution with a polarized target and a polarized final lepton

Abstract Lepton pair production at large transverse momentum in hadronic collisions is considered. Only one of the initial hadrons is polarized and the polarization of one of the leptons is detected, i.e. A B→ l − l + + X . General expressions of the squared amplitudes are presented. When A and B are protons, it is shown that in a proper range of the kinematic variables the process is a sensitive probe of the polarized gluon distribution.

Higgs boson production at large transverse momentum in hadronic collisions

Production of Higgs bosons accompanied by a large transverse momentum jet at hadron colliders via a top quark loop is calculated to lowest order QCD. Analytic expressions for the matrix elements, including the decay H → VV → four massless fermions (V = W,Z), are presented. The dependence of the matrix elements on the mass of the top quark exchanged in the loop in all regions of phase space is studied in detail. The Hj signal is compared with the background arising from VVj and V+3 jet production for LHC and SSC energies.

Quark gluon plasma and multiplicity dependence of transverse momentum in hadronic collisions

I propose experimental tests to examine the origin of the average <p T > dependence on hadron-hadron events multiplicity and to verify some possible implications of the existence of high-temperature phase transition to quark-gluon plasma. I suggest that evidences may already exist of this transition in SPS collider and ISR events with central rapidity density dn/dy within an interval of one or two units around 6.

Multiplicity of produced particles at large transverse momentum in hadronic collisions

The dependence of the multiplicity on transverse momentum and missing mass is discussed in the light of recent inclusive proton-proton experiments. The multiperipheral diagram in which a large-transverse-momentum particle is produced far from the ends of the chain is analyzed for the multiplicity as a function of transverse momentum. The multiplicity is found to decrease as a function of the transverse momentum of the large-transverse-momentum particle.

Multiplicity dependence of transverse momentum in hadronic collisions

The process of secondary-particle emission in hadron-hadron collisions is analytically studied using a simple model of hadron structure. The model neglects the 'size' of the hadron constituents, considering a hadron as a continuous distribution of matter according to a step function of radius R. A version of the eikonal approximation is applied to derive the relative probability for interaction and emission of secondaries when the impact parameter b is smaller than 2R. On the basis of these assumptions, and using the uncertainty relation, an empirical parameterization is obtained for the dependence of the transverse momentum of charged secondaries on their multiplicity in the case of high-energy proton-proton collisions. Comparison with experimental data at 28 GeV/c yields agreement to within about 3%. The analysis shows that at a fixed beam momentum, the transverse momentum decreases with increasing multiplicity, and that for a given multiplicity, the transverse momentum exhibits a slow increase with beam momentum.

Variation of transverse momentum in hadronic collisions

The paper presents a detailed parameterization of the transverse momentum in hadronic collisions on multiplicity and on beam momentum. Hadronic collisions are considered at energies below the ultra-high energy domain, on the basis of an uncertainty relation and a naive eikonal model with an impact-parameter-dependent multiplicity.