Forward Jet Production Research Articles

Forward gamma +jet production in proton-proton and proton-lead collisions at LHC within the FoCal calorimeter acceptance

Using the small-x improved transverse momentum dependent factorization (ITMD), which, for a general two-to-two massless scattering can be proved within the color glass condensate (CGC) theory for transverse momenta of particles greater than the saturation scale, we provide predictions for isolated forward photon and jet production in proton-proton and proton-nucleus collisions within the planned ALICE FoCal detector acceptance. We study azimuthal correlations, p_T spectra, as well as normalized ratios of proton-proton cross sections for different energies. The only TMD distribution needed for that process is the “dipole” TMD gluon distribution, which in our computations is based on HERA data and undergoes momentum space BK evolution equation with DGLAP corrections and Sudakov resummation. We conclude, that the process provides an excellent probe of the dipole TMD gluon distribution in saturation regime.

Single inclusive jet production in pA collisions at NLO in the small-x regime

We present the first complete next-to-leading-order (NLO) prediction with full jet algorithm implementation for the single inclusive jet production in pA collisions at forward rapidities within the color glass condensate (CGC) effective theory. Our prediction is fully differential over the final state physical kinematics, which allows the implementation of any infra-red safe observable including the jet clustering procedure. The NLO calculation is organized with the aid of the observable originated power counting proposed in [1] which gives rise to the novel soft contributions in the CGC factorization. We achieve the fully-differential calculation by constructing suitable subtraction terms to handle the singularities in the real corrections. The subtraction contributions can be exactly integrated analytically. We present the NLO cross section with the jets constructed using the anti-kT algorithm. The NLO calculation demonstrates explicitly the validity of the CGC factorization in jet production. Furthermore, as a byproduct of the subtraction method, we also derive the fully analytic cross section for the forward jet production in the small-R limit. We show that in the small-R approximation, the forward jet cross section can be factorized into a semi-hard cross section that produces a parton and the semi-inclusive jet functions (siJFs). We argue that this feature holds for generic jet production and jet substructure observables in the CGC framework. Last, we show numerical analyses of the derived formula to validate our calculations. We justify when the small-R approximation is appropriate. Like forward hadron production, the obtained NLO result also exhibits the negativity of the cross section in the large jet transverse regime, which signals the need for the threshold resummation. A sketch of the threshold resummation in the CGC framework is presented based on the multiple emission picture and it is found to agree with the approach using the rapidity renormalization group equation developed in [2].

Recent CMS results on soft and small-x QCD physics

We present latest results of soft and small-x QCD measurements with the CMS experiment, such as minimum bias/underlying event physics, and studies on forward jet production.

Forward Drell-Yan and backward jet production as a probe of the BFKL dynamics

We propose a new process which probes the BFKL dynamics in the high energy proton-proton scattering, namely the forward Drell-Yan (DY) production accompanied by a backward jet, separated from the DY lepton pair by a large rapidity interval. The proposed process probes higher rapidity differences and smaller transverse momenta than in the Mueller-Navelet jet production. It also offers a possibility of measuring new observables like lepton angular distribution coefficients in the DY lepton pair plus jet production.

Inclusive Forward-jet and Dijet Production at the LHC

Inclusive Forward-jet and Dijet Production at the LHC

Single and double inclusive forward jet production at the LHC ats=7and 13 TeV

We provide a description of the transverse momentum spectrum of single inclusive forward jets produced at the LHC, at the center-of-mass energies of 7 and 13 TeV, using the high energy factorization (HEF) framework. We subsequently study double inclusive forward jet production and, in particular, we calculate contributions to azimuthal angle distributions coming from double parton scattering. We also compare our results for double inclusive jet production to those obtained with the Pythia Monte Carlo generator. This comparison confirms that the HEF resummation acts like an initial state parton shower. It also points towards the need to include final state radiation effects in the HEF formalism.

Evidence forx-dependent proton color fluctuations inpAcollisions at the CERN Large Hadron Collider

We argue that the pattern of the deviation from the Glauber approximation prediction for the centrality dependence of the rate of forward jet production observed in pA collisions at the LHC provides the first experimental evidence that parton configurations in the projectile proton containing a parton with large $x$ interact with a nuclear target with a significantly smaller than average cross section and have smaller than average size. We implement the effects of fluctuations of the interaction strength and, using the ATLAS analysis of how hadron production at backward rapidities depends on the number of wounded nucleons, make quantitative predictions for the centrality dependence of the jet production rate as a function of the $x$-dependent interaction strength $\sigma(x)$. We find that \sigma(x)\sim 0.6 ~\sigma_{tot}(pp) gives a good description of the x=0.6 data and may shed a light on the origin of the EMC effect.

Cross sections and transverse single-spin asymmetries in forward jet production from proton collisions at [formula omitted

Measurements of the production of forward jets from transversely polarized proton collisions at s=500 GeV conducted at the Relativistic Heavy Ion Collider (RHIC) are reported. Our measured jet cross section is consistent with hard scattering expectations. Our measured analyzing power for forward jet production is small and positive, and provides constraints on the Sivers functions that are related to partonic orbital angular momentum through theoretical models.

Mueller–Navelet jets at LHC: BFKL versus high-energy DGLAP

The production of forward jets separated by a large rapidity gap at LHC, the so-called Mueller–Navelet jets, is a fundamental testfield for perturbative QCD in the high-energy limit. Several analyses have already provided us with evidence about the compatibility of theoretical predictions, based on collinear factorization and BFKL resummation of energy logarithms in the next-to-leading approximation, with the CMS experimental data at 7 TeV of center-of-mass energy. However, the question if the same data can be described also by fixed-order perturbative approaches has not yet been fully answered. In this paper we provide numerical evidence that the mere use of partially asymmetric cuts in the transverse momenta of the detected jets allows for a clear separation between BFKL-resummed and fixed-order predictions in some observables related with the Mueller–Navelet jet production process.

Forward jet production & quantum corrections to the gluon Regge trajectory from Lipatov’s high energy effective action

We review Lipatov’s high energy eective action and show that it is a useful computational tool to calculate scattering amplitudes in (quasi)-multi-Regge kinematics. We explain in some detail our recent work where a novel regularization and subtraction procedure has been proposed that allows to extend the use of this eective action beyond tree level. Two examples are calculated at next-to-leading order: forward jet vertices and the gluon Regge trajectory.

Measurements of forward jet production in polarized pp collisions at √s = 500 GeV

The AnDY project at RHIC was proposed to measure the analyzing power for Drell-Yan production. Test runs took place during polarized proton operations of RHIC in 2011 and 2012 with a model of the AnDY apparatus in place. In total, an integrated luminosity of 9 pb^-1 with beam polarization of 50% was sampled. The primary detector components were a hadron calorimeter (HCal) that spanned the pseudorapidity interval 2.4 < \eta < 4.0 and a small electromagnetic calorimeter (ECal). Basic goals for AnDY test running were to establish the impact of a third interaction region on RHIC performance and to demonstrate HCal calibration. Energy scale of HCal was established using neutral pion reconstruction and checked with hadronic response. In addition, data with a trigger based on HCal energy sum were taken to study jet events. First measurements of analyzing power in the forward jet production are reported.

MEASUREMENT OF FORWARD JETS AT RHIC

We present first measurements of forward jet production from p↑ + p collisions at [Formula: see text] GeV, including transverse single spin asymmetries. These asymmetries are expected to be sensitive to spin-correlated transverse momentum in the initial state, which is particularly interesting because it is related to orbital angular momentum in the proton.

Saturation in Central–Forward Jet Production in &lt;span class="cmmi-10"&gt;p&lt;/span&gt;–Pb Collisions at the LHC

Saturation in Central–Forward Jet Production in &lt;span class="cmmi-10"&gt;p&lt;/span&gt;–Pb Collisions at the LHC

Measurements of forward energy flow and forward jet production with CMS

We present measurements of the forward (3 < |η| < 5) energy flow in minimum bias events and in events with either hard jets or W and Z bosons produced at central rapidities, as well as measurements of the inclusive forward jet cross section and of associated production of forward and central jets. Results are compared to MC models with different parameter tunes for the description of the underlying event and to perturbative QCD calculations, the PYTHIA and HERWIG parton shower event generators, as well as to the CASCADE Monte Carlo.

Particle production at HERA

Results on particle production in deep-inelastic scattering in ep collision at HERA, obtained with the H1 and ZEUS detectors, are presented. The underlying parton dynamics is investigated by studying the transverse momentum distribution of charged particles and comparing the measurements with various Monte Carlo generators using different approaches to simulate the parton cascade. In this context also results on forward jet production are discussed. The underlying parton dynamics is also studied using prompt photon production in both DIS and photoproduction regimes. The production is compared to theoretical calculations and Monte Carlo predictions. In the context of hadronisation, studies are presented of the scaled momentum distribution for charged hadrons and for K S 0 and Λ particles in the current fragmentation region of the Breit frame. The data are compared to models and to next-to-leading order QCD calculations. In addition, differential cross sections for K S 0 production in the laboratory and Breit frame are investigated and compared to Monte Carlo predictions, which are used to study the flavour decomposition and strangeness suppression factor. K S 0 production is also compared to the production of charged particles and to the production rate of the DIS events.

Forward Physics Hard Processes and Saturation: Theory and Phenomenology Review

Selected aspects of the theory and phenomenology of production of forward jets at the LHC and RHIC are overviewed. In the theory part we discuss basics of frameworks originating from the BFKL dynamics while in the phenomenology part we present results for forward-central jet correlations at the LHC and forward di-jet production at RHIC.

Highlights in Forward Physics from CMS

A few CMS analyses based on data collected during 2009–2010 data taking period are reviewed, including forward jet production cross-section measurements, energy flow measurement for Minimum Bias events as well as for events with presence of hard scale, and observation of single diffraction.

Forward jet-like event spin-dependent properties in polarized p + p collisions at √s = 200 GeV

The STAR collaboration has reported precision measurements on the transverse single spin asymmetries for the production of forward π0 mesons from polarized proton collisions at √s = 200 GeV. To disentangle the contributions to forward asymmetries, one has to look beyond inclusive π0 production to the production of forward jets or direct photons. Present forward detector capabilities are not well matched to the complete reconstruction of forward jets, but do have sufficient acceptance for "jet-like" events."Jet-like" events are the clustered response of an electromagnetic calorimeter that is primarily sensitive to incident photons, electrons and positrons. During the RHIC running in the year 2006, STAR with the Forward Pion Detector (FPD++) in place collected 6.8 pb−1 of data with an average polarization of 60 %. FPD++ was a modular detector prototype of the Forward Meson Spectrometer (FMS) that consisted of two detectors placed symmetrically with respect to the beam line at a distance of 7.4 m from the interaction point. Readout of the FPD++ was triggered when the sum of energies in the central module of the calorimeter used for π0 measurements was larger than a threshold. This trigger minimizes the bias for "jet-like" events, making it appropriate to disentangling contributions to the forward transverse spin asymmetries. We report on the status of the analysis.

Measurement of forward jets, forward energy flow and diffractive events with CMS

Abstract We report on a first measurement of forward jet production and forward energy flow in pp collisions up to highest energies of s = 7 TeV . Inclusive spectra of jets are presented with p t > 20 GeV in the region of 3 | η | 5 . The energy flow in the forward region is measured for minimum bias events and for events with a high p t dijet in the central region. In addition, the absence of energy deposition in the forward region is used to observe diffractive events. We compare our results with predictions from Monte Carlo event generators including a simulation of multi-parton scattering.

Forward and Mueller-Navelet Jets

We discuss the production of forward jets in high energy processes where one probes a dense hadronic wavefunction. In particular, and as a signature of parton saturation, we discuss the possibility of a strong momentum decorrelation in Mueller-Navelet jets which leads to a geometric scaling behavior.