We compare results of $k_t$-factorization approach and next-to-leading order collinear-factorization approach for photon-jet correlations in $pp$ and $p \bar p$ collisions at RHIC, Tevatron and LHC energies. We discuss correlations in azimuthal angle between photon and jet as well as correlations in two-dimensional space of photon and jet transverse momenta. Different unintegrated gluon/parton distributions are used in the $k_t$-factorization approach. The results depend on UGDF/UPDF used. The collinear NLO $2 \to 3$ contributions dominate over $k_t$-factorization cross section at small relative azimuthal angles as well as for asymmetric transverse momentum configurations.
We make an analysis of the hadronic invariant mass spectrum in inclusive charmless semileptonic B meson decays in a QCD-based approach. The decay width is studied as a function of the invariant mass cut. We examine their sensitivities to the parameters of the theory. The theoretical uncertainties in the determination of $|V_{ub}|$ from the hadronic invariant mass spectrum are investigated. A strategy for improving the theoretical accuracy in the value of $|V_{ub}|$ is described.
We summarize the studies on the hadronic production of S- and P-wave $(\bar bc)$ mesons via direct fragmentation of the bottom antiquark as well as the Altarelli-Parisi induced gluon fragmentation.
We investigate the single-spin asymmetries in inclusive and exclusive processes of electron-proton scattering and electron-positron annihilation. In the decomposition of hadronic tensor, a Lorentz symmetric spin-dependent term is generally present. The existence of such a term implies single-spin asymmetries in these processes and these single-spin asymmetries for baryons can be understood in a unified manner. We argue that it is important to measure the single-spin asymmetries in both inclusive and exclusive processes for the $Λ$ production at the present B-factories. This will lead to the fi…
We evaluate the inclusive semileptonic B decay spectrum as a function of the final-state hadrons energy to second order in the inverse quark mass expansion and tree level in $α_{s}$. We argue that there is an energy interval below the $c$ production threshold that could be used to determine $V_{ub}$.
We consider in the soft-collinear effective theory semi-inclusive hadronic B decays, B-> XM, in which an energetic light meson M near the endpoint recoils against an inclusive jet X. We focus on a subset of decays where the spectator quark from the B meson ends up in the jet. The branching ratios and direct CP asymmetries are computed to next-to-leading order accuracy in alpha_s and to leading order in 1/m_b. The contribution of charming penguins is extensively discussed, and a method to extract it in semi-inclusive decays is suggested. Subleading 1/m_b corrections and SU(3) breaking effects a…
After giving their general expressions valid at all x, double differential 1-particle inclusive distribution inside a quark and a gluon jet produced in a hard process, together with the inclusive kt distribution, are given at small x in the Modified Leading Logarithmic Approximation (MLLA), as functions of the transverse momentum kt of the outgoing hadron.
By examining the symmetry constraints on the semi-inclusive pseudoscalar particle production in unpolarized inelastic lepton-hadron scattering, we present a complete, exact Lorentz decomposition for the corresponding hadronic tensor. As a result, we find that it contains five independent terms, instead of the four as have been suggested before. The newly identified one is odd under the naive time reversal transformation, and the corresponding structure function is directly related to the single spin asymmetry in the semi-inclusive pseudoscalar meson production by a polarized lepton beam off an…
The dispersive approach to QCD is applied to the study of the inclusive tau lepton hadronic decay. This approach provides the unified integral representations for the hadronic vacuum polarization function, related R function, and Adler function. These representations account for the intrinsically nonperturbative constraints, which originate in the kinematic restrictions on the functions on hand, and retain the effects due to hadronization, which play a valuable role in the analysis of the strong interaction processes at low energies. The dispersive approach proves to be capable of describing r…
Minijet production in jet inclusive cross sections at hadron colliders, with large rapidity intervals between the tagged jets, is evaluated by using the BFKL pomeron. We describe the jet inclusive cross section for an arbitrary number of tagged jets, and show that it behaves like a system of coupled pomerons.
The dispersive approach to QCD, which properly embodies the intrinsically nonperturbative constraints originating in the kinematic restrictions on relevant physical processes and extends the applicability range of perturbation theory towards the infrared domain, is briefly overviewed. The study of OPAL (update 2012) and ALEPH (update 2014) experimental data on inclusive tau lepton hadronic decay in vector and axial-vector channels within dispersive approach is presented.
In a perturbative QCD approach, with inclusion of spin and transverse momentum effects, experimental data on azimuthal asymmetries observed in polarized semi-inclusive deeply inelastic scattering and e+ e- annihilations can be used to determine the Sivers, transversity and Collins soft functions. By using these functions, within the same scheme, we predict p(transv. polarized) p -> h + X single spin asymmetries in remarkable agreement with RHIC experimental data.
We study jet angularity measurements for single-inclusive jet production at the LHC. Jet angularities depend on a continuous parameter $a$ allowing for a smooth interpolation between different traditional jet shape observables. We establish a factorization theorem within Soft Collinear Effective Theory (SCET) where we consistently take into account in- and out-of-jet radiation by making use of semi-inclusive jet functions. For comparison, we elaborate on the differences to jet angularities measured on an exclusive jet sample. All the necessary ingredients for the resummation at next-to-leading…
We summarize our calculation of the total cross section for top quark production at hadron colliders within the context of perturbative quantum chromodynamics, including resummation of the effects of initial-state soft gluon radiation to all orders in the strong coupling strength.
We calculate the one-loop QCD correction for inclusive jet cross section and Drell-Yan process in a general low-energy effective Lagrangian for composite quarks and leptons.
We apply the theory of parton-parton total cross sections at large ``s", due to Lipatov and collaborators, to compute the inclusive cross section for jets which accompany a large ``s" parton scattering process.
Light-cone dominance is established for a particular set of semi-inclusive observables in $e^+ e^-$ hadronic annihilation. This allows to deduce, with a certain degree of rigor, the angular distribution of hadronic energy from first principles, without invoking quark-hadron duality.
We calculate the hadronic tensor for inclusive semileptonic B decay to O(alpha_s). This allows O(alpha_s Lambda_{QCD}/mb) corrections to hadronic invariant mass observables to be directly evaluated with experimentally required cuts on phase space. Several moments of phenomenological interest are presented to O(alpha_s Lambda_{QCD}/mb) and O(Lambda_{QCD}^3/mb^3), allowing a consistent extraction of the HQET parameters up to O(Lambda_{QCD}^3/mb^3) and the b quark mass with theoretical error ~ 50 MeV. The hadronic invariant mass spectrum is examined with a general moment to obtain observables tha…
Inclusive distributions of soft production of mesons in hadronic collisions are calculated in the valon-recombination model. The new determination of the valon distributions from hard scattering data makes possible a tightly interrelated treatment of pion and kaon production in the fragmentation regions of proton, pion and kaon. Only one free parameter is used in the determination of the valon distribution in the kaon. No other adjustable parameter is needed to fit the $x$-distributions of the data on inclusive cross sections, except for the normalizations since the data are at fixed $p_T$. Th…
We provide complete analytic expressions for the inclusive prompt photon production cross section in hadronic final states of $e^+e^-$ annihilation reactions through one-loop order in quantum chromodynamics perturbation theory. Computed explicitly are direct photon production through first order in the electromagnetic strength $α_{em}$ and the quark-to-photon and gluon-to-photon fragmentation contributions through first order in the strong coupling $α_s$. The full angular dependence of the cross sections is displayed, separated into transverse $(1 +\cos ^2θ_γ)$ and longitudinal $(\sin ^2θ_γ)$ …
A QCD formula for the polarization in the large-p_T Λhyperon production in the unpolarized nucleon-nucleon collision at large x_F is derived. We focus on the mechanism in which the chiral-odd spin-independent twist-3 quark distribution E_F(x,x) becomes the source of the transversely polarized quarks fragmenting into the polarized Λ. A simple model estimate for that contribution shows the possibility that it gives rise to a sizable Λpolarization.
Recent progress in application of higher order QCD calculations to jet and inclusive particle production in photon induced collisions is reviewed. Attention is paid to theoretical uncertainties of such calculations, particularly those coming from the choice of renormalization and factorization scales.
Inclusive jet production in p-p and pbar-p collisions shows many of the same kinematic systematics as observed in single particle inclusive production at much lower energies. In an earlier study (1974) a phenomenology, called radial scaling, was developed for the single particle inclusive cross sections that attempted to capture the essential underlying physics of point-like parton scattering and the fragmentation of partons into hadrons suppressed by the kinematic boundary. The phenomenology was successful in emphasizing the underlying systematics of the inclusive particle productions. Here w…
We have calculated inclusive two-jet cross sections in next-to-leading order QCD for low Q^2 ep collisions superimposing direct and resolved contributions. Infrared and collinear singularities in the virtual and real contributions are cancelled with the phase space slicing method. Various inclusive two-jet distributions have been computed. The results are compared with recent data from the ZEUS collaboration at HERA.
The QCD predictions for single-inclusive jet production are computed with joint resummation of threshold and jet radius logarithms. The results are compared to those based on fixed order perturbation theory up to next-to-next-to-leading order and to data by the CMS collaboration measured in proton-proton collisions at the LHC at $\sqrt{S}=8$ TeV. The joint resummation results are in remarkable agreement with the data.
In this paper, we report our results on charged hadron multiplicities of heavy quark initiated jets produced in high energy collisions. After implementing the so-called dead cone effect in QCD evolution equations, we find that the average multiplicity decreases significantly as compared to the massless case. Finally, we discuss on the transverse momentum distribution of light quark initiated jets and emphasize on the comparison between our predictions and CDF data.
The dispersive approach to QCD and its applications to inclusive tau lepton hadronic decay and hadronic vacuum polarization function are briefly discussed.
Known perturbative expressions for the decay rates of 115 GeV Higgs particle into either two gluons or a $b\bar{b}$ pair are shown to exhibit renormalization-scale-($μ$)-dependence that is largely removed via renormalization-group/Pade-approximant estimates of these rates' next order contributions. The extrema in $μ$ characterizing both rates, as determined from fully-known orders of perturbation theory, are very nearly equal to corresponding $μ$-insensitive rates obtained via estimation of their next order contributions, consistent with "minimal-sensitivity" expectations.
We derive generating functions, valid to next-to-double logarithmic accuracy, for QCD jet rates according to the inclusive forms of the kt, Cambridge/Aachen and anti-kt algorithms, which are equivalent at this level of accuracy. We compare the analytical results with jet rates and average jet multiplicities from the SHERPA event generator, and study the transition between Poisson-like and staircase-like behaviour of jet ratios.
The hadronic $\kt$-spectrum and the gluon to quark average multiplicity ratio $r=N_g/N_q$ inside a high energy sub-jet are determined from a precise definition of the jet axis, including corrections of relative magnitude ${\cal O}(\sqrt{α_s})$ with respect to the Modified Leading Logarithmic Approximation (MLLA), in the limiting spectrum approximation (assuming an infrared cut-off $Q_0 =\lqcd$). The results for the $\kt$-spectrum in the limiting spectrum approximation are found to be, after normalization, in impressive agreement with measurements by the CDF collaboration and the ratio has not …
The inclusive production of several jets is studied in the framework of the hard pomeron model. The average jet momenta are found to be strongly ordered and growing towards the central c.m. rapidity, as expected. Strong positive correlations are found for pairs of jets neighbouring in rapidity, both in the forward-backward and forward-forward directions.
We discuss the theory of inclusive production of heavy quarkonium, the comparison between theory and experiment, and the expected nuclear effects in cold nuclear targets. We also present predictions, based on Nonrelativistic QCD (NRQCD), for quarkonium production cross sections in the LHC energy range. We find that nuclear effects in the production cross sections are largely independent of the sizes of the NRQCD matrix elements, the charmonium state that is produced and, in the color-octet case, largely independent of the partonic subprocess that produces the heavy quark-antiquark pair.
We present the calculation for single-inclusive jet production in (longitudinally) polarized deep-inelastic lepton-nucleon scattering at next-to-next-to leading order (NNLO) accuracy, based on the Projection-to-Born method. As a necessary ingredient to achieve the NNLO results, we also introduce the next-to-leading-order (NLO) calculation for the production of di-jets in polarized DIS. Our di-jet calculation is based on an extension of the dipole subtraction method to account for polarized initial-state partons. We analyze the phenomenological consequences of higher order QCD corrections for t…
Uncertainties in the NLO calculation of the inclusive jet cross section due to the choice of renormalization scale, parton distribution functions and clustering algorithm are explored. These are found to be similar in size to the current experimental uncertainties of the measured inclusive jet cross section at DZero and CDF.
We study one-jet inclusive hadro-production and compute the QCD threshold corrections for large transverse momentum of the jet in the soft-gluon resummation formalism at next-to-leading logarithmic accuracy. We use the resummed result to generate approximate QCD corrections at next-to-next-to leading order, compare with results in the literature and present rapidity integrated distributions of the jet's transverse momentum for Tevatron and LHC. For the threshold approximation we investigate its kinematical range of validity as well as its dependence on the jet's cone size and kinematics.
In this paper we briefly review some examples of inclusive energy-momentum distributions and correlations in QCD intra-jet cascades. Emphasis is given to the role of gluon coherence effects in final states hadron spectra. These observables provide tests of the Local Parton Hadron Duality (LPHD) hypothesis.
DIS on a two nucleon system in the regge limit is considered. In this framework a review is given of a pQCD approach for the computation of the corrections to the inclusive one jet production cross section at finite number of colors and discuss the general results.
We have calculated inclusive one-- and two--jet production in photon--photon collisions in next--to--leading order superimposing direct, single resolved and double resolved cross sections. The results are compared with recent experimental data from the TOPAZ and AMY collaborations at TRISTAN. Good agreement is found between experiment and the theoretical results.
The role of intrinsic transverse momentum both in unpolarized and polarized processes is discussed. We consider inclusive cross sections for pion production in hadronic collisions and for Drell-Yan processes. We reanalyze transverse single spin asymmetries (SSA) in inclusive pion production, p(transv. polarized) p --> pion + X, in terms of Sivers effect and show its contribution to A_{UL} in semi-inclusive DIS (SIDIS).
In this paper we investigate the hadronic mass spectra of inclusive B decays. Specifically, we study how an upper cut on the invariant mass spectrum, which is necessary to extract V_{ub}, results in the breakdown of the standard perturbative expansion due to the existence of large infrared logs. We first show how the decay rate factorizes at the level of the double differential distribution. Then, we present closed form expressions for the resummed cut rate for the inclusive decays B -> X_s gamma and B -> X_u e nu at next-to-leading order in the infrared logs. Using these results, we determine…
Using the recently found hA amplitude, single and double inclusive jet production rates on the nucleus are studied in the perturbative QCD with $N_c\to\infty$. Jet multiplicities are found to grow with $A$ and energy as $A^{2/9}s^Δ$ where $Δ$ is the BFKL intercept. Long range correlations are found to behave as $A^{4/9}s^{2Δ}$ and change from negative to positive at a certain high energy.
We propose the study of new observables in LHC inclusive events with three tagged jets, one in the forward direction, one in the backward direction and both well-separated in rapidity from the each other (Mueller-Navelet jets), together with a third jet tagged in central regions of rapidity. Since non-tagged associated mini-jet multiplicity is allowed, we argue that projecting the cross sections on azimuthal-angle components can provide several distinct tests of the BFKL dynamics. Realistic LHC kinematical cuts are introduced.
We have calculated inclusive one-- and two--jet production in photon--photon collisions superimposing direct, single resolved and double resolved cross sections for center of mass energies of the LEP1, LEP2 and NLC range. The direct and single resolved cross sections are calculated up to next--to--leading order. The double resolved two--jet cross section is calculated only in LO with a $k$ factor estimated from the NLO one--jet cross section. Various differential cross sections as functions of transverse momenta and rapidities of the jets are evaluated.
We have calculated inclusive two-jet production in photon-photon collisions superimposing direct, single-resolved and double-resolved cross sections for center-of-mass energies of TRISTAN and LEP1.5. All three contributions are calculated up to next-to-leading order. The results are compared with recent experimental data. Three NLO sets of parton distributions of the photon are tested.
We study the single jet inclusive cross section up to next-to-next-to leading order in perturbative QCD, implemented in the parton-level event generator NNLOJET . Our results are fully differential in the jet transverse momentum and rapidity and we apply fiducial cuts for comparison with the available ATLAS 7 TeV 4.5 fb$^{-1}$ data for jet radius $R=0.4$. For the theoretical calculation we employ the antenna subtraction method to reliably cancel all infrared divergences present at intermediate stages of the calculation. We present all results using the individual jet transverse momentum $μ_{R}…
In this report, we give the Balitsky Fadin Kuraev Lipton formalism for jet gap jet events at hadronic colliders. We also discuss the case where in addition at least one proton is intact in the final state in diffractive events.
The recently reported CDF and D0 inclusive jet cross-sections are compared, using a uniform theoretical NLO QCD calculation to account for the different kinematic coverages of the pseudo-rapidity variable in the two experiments. The two data sets are found to be in good agreement. With a 2-3\% relative overall normalization adjustment, the data sets appear to agree over the entire $E_t$ range, even without taking into account the other systematic errors.
After demonstrating their general expressions valid at all x, double differential 1-particle inclusive distributions inside a quark and a gluon jet produced in a hard process, together with the inclusive k-transverse distributions, are calculated at small x in the Modified Leading Logarithmic Approximation (MLLA), as functions of the transverse momentum of the outgoing hadron. Results are compared with the Double Logarithmic Approximation (DLA) and a naive DLA-inspired evaluation; sizable corrections are exhibited which, associated with the requirement to stay in a perturbative regime, set the…
High statistics fixed target and ISR inclusive photon production data are compared to next-to-leading order (NLO) QCD calculations. The dependence of the theoretical predictions on the structure functions, and on the theoretical scales is investigated. It is shown that the data cannot be simultaneously fitted with a single set of structure functions and scales. However, it is argued that as long as one restricts the data/theory comparison to the xT range where the theory is reliable, i.e. stable with respect to the scale variation, there is no need to introduce an additional primordial kT depe…
We discuss fixed target and ISR inclusive photon production and attempt a comparison between theory and experiments. The dependence of the theoretical predictions on the structure functions, and on the renormalization and factorization scales is investigated. The main result of this study is that the data cannot be simultaneously fitted with a single set of scales and structure functions. On the other hand, there is no need for an additional intrinsic $k_{_T}$ to force the agreement between QCD predictions and experiments, with the possible exception of one data set. Since the data cover almos…
Single and double inclusive cross-sections for gluon jet production from within the triple pomeron vertex are studied in the reggeized gluon technique. It is shown that to satisfy the AGK rules the vertex has to be fully symmetric in all four reggeized gluons which form the two final pomerons. The single inclusive cross-sections are found for different cuttings of the triple pomeron vertex. They sum into the expression obtained by Yu.Kovchegov and K.Tuchin in the colour dipole picture. The found double inclusive cross-sections satisfy the AGK rules.
The inclusive transverse momentum (pt) distribution of hadrons inside jets produced in PbPb and pp collisions are simulated with the YaJEM and Pythia 6 Monte Carlo (MC) event generators. The effects of jet quenching are studied via the ratios of PbPb over pp hadron pt spectra, either by accounting for the induced virtuality Delta Q^2 transferred from the strongly-interacting medium to the parton shower or by modifying the soft sector of the parton-to-hadron fragmentation functions. The MC results are compared to experimental jet data measured by the CMS experiment at a center-of-mass energy of…
A next-to-leading order QCD calculation for single-inclusive jet photoproduction in unpolarized and longitudinally polarized lepton-hadron collisions is presented which consistently includes ``direct'' and ``resolved'' photon contributions. The computation is performed within the ``small-cone approximation'' in a largely analytical form. Phenomenological aspects of jet production at future ep colliders such as the CERN-LHeC and the polarized BNL-eRHIC are discussed, placing particular emphasis on the perturbative stability of the predictions and the possibility to constrain the parton content …
We propose the study of new observables in LHC inclusive events with three tagged jets, one in the forward direction, one in the backward direction and both well-separated in rapidity from the each other (Mueller-Navelet jets), together with a third jet tagged in central regions of rapidity. Since non-tagged associated mini-jet multiplicity is allowed, we argue that projecting the cross sections on azimuthal-angle components can provide several distinct tests of the BFKL dynamics. Realistic LHC kinematical cuts are introduced.
The inclusive cross-section for production of a jet with a given transverse momentum off a heavy nucleus is derived in the BFKL framework with a running coupling on the basis of the bootstrap relation. The cross-section depends on the same three different coupling constants as the total cross-section unlike the cross-section for gluon production derived in the dipole approach.
In the framework of perturbative QCD, double inclusive cross sections for high $p_t$ parton production in nucleus-nucleus collisions are computed with multiple rescattering taken into account. The induced long-range correlations between numbers of jets at forward and backward rapidities are found to reach $10÷20$% for light nuclei at $\sqrt{s}=200$ GeV/c and to be suppressed for heavy nuclei and LHC energies.
A method to facilitate the consistent inclusion of cross-section measurements in proton parton density functions (PDFs) fits in NLO QCD has been developed. It allows the a posteriori variation of the renormalisation and factorisation scales and of the centre-of-mass energy and the inclusion of arbitrary PDFs, strong coupling in cross-section calculations. The theoretical uncertainties in the double differential single inclusive jet cross-section at a $\sqrt{s}=7$ TeV have been studied using this method.
We present the first calculation of inclusive jet production in deep-inelastic scattering with approximate next-to-next-to-leading order (aNNLO) contributions, obtained from a unified threshold resummation formalism. The leading coefficients are computed analytically. We show that the aNNLO contributions reduce the theoretical prediction for jet production in deep-inelastic scattering, improve the description of the final HERA data in particular at high photon virtuality Q^2 and increase the central fit value of the strong coupling constant.
We suggest the inclusive detection at the LHC of a light charged hadron and of a jet widely separated in rapidity as a new probe channel for the study of the BFKL resummation. Predictions for cross section and azimuthal correlations, shaped on the CMS and CASTOR acceptances, are presented.
We discuss the correlated systematic theoretical uncertainties that may be ascribed to the next-to-leading order QCD theory used to predict the one-jet inclusive cross section in hadron collisions. We estimate the magnitude of these errors as functions of the jet transverse momentum and rapidity. The total theoretical error is decomposed into a set of functions of transverse momentum and rapidity that give a model for statistically independent contributions to the error. This representation can be used to include the systematic theoretical errors in fits to the experimental data.
