We study the lepton-jet correlation in deep inelastic scattering. We perform one-loop calculations for the spin averaged and transverse spin dependent differential cross sections depending on the total transverse momentum of the final state lepton and the jet. The transverse momentum dependent (TMD) factorization formalism is applied to describe the relevant observables. To show the physics reach of this process, we perform a phenomenological study for HERA kinematics and comment on an ongoing analysis of experimental data. In addition, we highlight the potential of this process to constrain small-$x$ dynamics.
We suggest that, if current measurements of inclusive jet production for central rapidities at the LHC are extended to lower transverse momenta, one could define a visible cross section sensitive to the unitarity bound set by the recent determination of the inelastic proton-proton cross section.
We propose the lepton-jet correlation in deep inelastic scattering as a unique tool for nucleon/nucleus tomography at the electron-ion collider. The azimuthal angular correlation between the final state lepton and jet depends on the transverse momentum dependent quark distributions. We take the example of single transverse spin asymmetries to show the sensitivity to the quark Sivers function. When the correlation is studied in lepton-nucleus collisions, transverse momentum broadening effects can be used to explore cold nuclear matter effects. These features make lepton-jet correlations an impo…
We propose a factorized approach to QED radiative corrections for inclusive and semi-inclusive deep-inelastic scattering to systematically account for QED and QCD radiation contributions to both processes on equal footing. This is achieved by utilizing factorization to resum logarithmically enhanced QED radiation into universal lepton distribution and fragmentation (or jet) functions. Numerical simulations suggest that the QED effects induced by the rotational distortion of the hadron transverse momentum, arising from the mismatch between the experimental Breit frame and the true photon-hadron…
We study charged lepton flavor violation (CLFV) associated with heavy quark pair production in lepton-nucleon deep-inelastic scattering $\ell_i N \to \ell_j q\bar{q} X$. Here $\ell_i$ and $\ell_j$ denote the initial and final leptons; $N$ and $X$ are respectively the initial nucleon and arbitrary final hadronic system. We employ a model Lagrangian in which a scalar and pseudoscalar mediator generates the CLFV. We derive heavy quark structure functions for scalar and pseudoscalar currents and compute momentum distributions of the final lepton for the process. Our focus is on the heavy quark mas…
Predictions for semi-inclusive deep inelastic lepton-nucleus scattering are presented. Both the effects of gluon radiation by the struck quark and the absorption of the produced hadron are considered. The gluon radiation covers a larger window in virtuality $Q^2$ because of the increased deconfinement of quarks inside nuclei. The absorption of hadrons formed inside the nucleus is described with a flavor dependent cross section. Calculations for rescaled fragmentation functions and nuclear absorption are compared with the EMC and HERMES data for N, Cu and Kr targets with respect to the deuteron…
We consider the spin polarization of leptons produced in neutrino and antineutrino nucleon deep inelastic scattering, via charged currents, and we study the positivity constraints on the spin components in a model independent way. These results are very important, in particular in the case of $τ^{\pm}$ leptons, because the polarization information is crucial in all future neutrino oscillation experiments.
The $O(α)$ leptonic QED corrections to neutral current polarized deep inelastic lepton-nucleon scattering are calculated in leptonic variables both for the case of longitudinal and transverse nucleon polarization. The results of the complete calculation are compared with the corresponding leading log expressions. Numerical results are presented for the corrections in the kinematic range of the HERMES experiment and possible future polarized proton beam experiments at HERA.
The one-loop electroweak radiative correction of the lowest order to lepton current for deep inelastic scattering of longitudinally polarized leptons by polarized nucleons is obtained in model independent way. The detailed numerical analysis within kinematical requirements of future polarization collider experiments is performed. The possibility to reduce radiative effects by detection of hard photons is studied.
The contribution of the radiative tail from the quasielastic peak to low order radiative correction to deep inelastic scattering of polarized leptons by polarized $^3$He was calculated within the sum rules formalism and $y$-scaling hypothesis. Numerical analysis was carried out under the conditions of HERMES experiment.
The perturbative QCD predictions concerning deep inelastic scattering at low $x$ are summarized. The theoretical framework based on the leading log $1/x$ resummation and $k_t$ factorization theorem is described. The role of studying final states in deep inelastic scattering for revealing the details of the underlying dynamics at low $x$ is emphasised and some dedicated measurements, like deep inelastic scattering accompanied by an energetic jet, the measurement of the transverse energy flow and deep inelastic diffraction, are briefly discussed.
We calculate the O(α_s) corrections to the production of a hard and isolated photon accompanied by one or two jets in deep inelastic lepton nucleon scattering at HERA. Numerical results are presented and the potential of this process for studies of parton distribution functions is discussed.
We suggest a new class of tests for searching for lepton flavor non-universality (LFNU) using ratio observables and based on correlations among the underlying LFNU new physics (NP) effects in several (seemingly independent) di-lepton and single lepton + jet(s) processes. This is demonstrated by studying the effects generated by LFNU 4-Fermi interactions involving 3rd generation quarks. We find that the sensitivity to the scale ($Λ$) of the LFNU 4-Fermi operators significantly improves when the correlations among the various di-lepton +jets and single-lepton + jets processes are used, reaching …
Main nuclear corrections for inelastic scattering of charged leptons on nuclei, namely shadowing, EMC-effect and Fermi motion have been investigated. Simple formulas describing these effects for different x-regions have been proposed, and unified expression for any transferred energy and momentum as well as for different nuclei has been obtained. Results of calculations of the ratio of nucleus structure function (per nucleon) and free nucleon structure function are in a good agreement with SLAC data.
We propose a new jet algorithm for deep-inelastic scattering (DIS) that accounts for the forward-backward asymmetry in the Breit frame. The Centauro algorithm is longitudinally invariant and can cluster jets with Born kinematics, which enables novel studies of transverse-momentum-dependent observables. Furthermore, we show that spherically-invariant algorithms in the Breit frame give access to low-energy jets from current fragmentation. We propose novel studies in unpolarized, polarized, and nuclear DIS at the future Electron-Ion Collider.
We discuss the close relation between shadowing in deep-inelastic lepton-nucleus scattering and diffractive photo- and leptoproduction of hadrons from free nucleons. We show that the magnitude of nuclear shadowing at small Bjorken-x, as measured by the E665 and NMC collaborations, is directly related to HERA data on the amount of diffraction in the scattering from free nucleons.
In this paper we extend the calculation of the QED corrections to deep inelastic lepton-proton scattering with a tagged photon, taking into account the full corrections on the lepton side. Comparing to previous results that were obtained by considering only large logarithmic terms at leading and next-to-leading accuray, we find that the difference is in general quite small, however, it may be significant in the region of large $y$ and small $x$.
The contribution of lepton and photon pair production in ep-scattering to the cross section of semi-inclusive deep inelastic scattering ep-> e'p'X has been calculated. The numerical results showed a large contribution of this processes at $ϕ_h=180^o$, in a good agreement with preliminary experimental data.
A precision measurement of jet cross sections in neutral current deep-inelastic scattering for photon virtualities $5.5<Q^2<80\,{\rm GeV}^2$ and inelasticities $0.2<y<0.6$ is presented, using data taken with the H1 detector at HERA, corresponding to an integrated luminosity of $290\,{\rm pb}^{-1}$. Double-differential inclusive jet, dijet and trijet cross sections are measured simultaneously and are presented as a function of jet transverse momentum observables and as a function of $Q^2$. Jet cross sections normalised to the inclusive neutral current DIS cross section in the respective $Q^2$-i…
We give an overview of jet physics in deeply inelastic scattering at HERA. The problem of jet definitions, the scale dependence of jet cross sections and some applications are discussed. (Talk presented at the Workshop on Deeply Inelastic Scattering and QCD, Paris, April 1995. To appear in the proceedings.)
A first measurement of the 1-jettiness event shape observable $τ_1^b$ in neutral-current deep inelastic scattering is presented. For the measurement, the equivalence of $τ_1^b$ to the DIS thrust observable defined in the Breit frame is utilised. The data were taken by the H1 experiment at HERA from 2003 to 2007 at a centre of mass energy of $\sqrt{s}=319 \text{ GeV}$. The data amount to an integrated luminosity of $351.6\text{ pb}^{-1}$. The triple-differential cross sections are presented as a function of the 1-jettiness $τ^1_b$, the virtuality of the exchanged boson $Q^2$ and the inelasticit…
We calculate the polarization of Lambda and Anti-Lambda particles produced in deep inelastic polarized lepton scattering. We use two models: the naive quark model and a model in which SU(3)$_F$ symmetry is used to deduce the spin structure of SU(3) octet hyperons from that of the proton. We perform the calculations for Lambda and Anti-Lambda produced directly or as decay products of $Σ^0$ and $Σ^*$.
The recent results of Forshaw and Sabio Vera on small-$x$ jet rates to order $α_s^3$ are extended to all orders, for any number of jets. A simple generating function is obtained.
We calculate shadowing in the process of deep inelastic interactions of leptons with nuclei in the perturbative regime of QCD. We find appreciable shadowing for heavy nuclei (e.g. Pb) in the region of small Bjorken scaling variable $10^{-5}\leq x \leq 10^{-3}$. This shadowing depends weakly on $Q^2$, but it may be strongly influenced, especially at $x \geq 10^{-3}$, by the existence of real parts of the forward scattering amplitudes.
We use the BFKL equation to calculate the rate of deep inelastic scattering events containing two forward jets (adjacent to the proton remnants) at HERA. We compare the production of two forward jets with that of only one forward jet (the "Mueller" process). We obtain a stable prediction for this two to one jet ratio, which may serve as a measure of the BFKL vertex function.
We perform a χ^2-analysis of Nuclear Parton Distribution Functions (NPDFs) using neutral current charged-lepton Deeply Inelastic Scattering (DIS) and Drell-Yan data for several nuclear targets. The nuclear A dependence of the NPDFs is extracted in a next-to-leading order fit. We compare the nuclear corrections factors F2(Fe)/F2(D) for this charged-lepton data with other results from the literature. In particular, we compare and contrast fits based upon the charged-lepton DIS data with those using neutrino-nucleon DIS data.
We study the azimuthal angle decorrelation of forward jets in Deep Inelastic Scattering. We make predictions for this observable at HERA describing the high energy limit of the relevant scattering amplitudes with quasi-multi-Regge kinematics together with a collinearly improved evolution kernel for multiparton emissions.
For theoretically consistent determination of $α_s$ from jet rates in deep inelastic scattering the dependence on $α_s$ of parton distribution functions is in principle as important as that of hard scattering cross--sections. For the kinematical region accessible at HERA we investigate in detail numerical importance of these two sources of the $α_s$ dependence of jet rates.
We extend the calculations of the spin alignments of vector mesons in $e^+e^-$ annihilation in a recent Rapid Communication to deeply inelastic lepton-nucleon scatterings. We present the results for different mesons in the current fragmentation regions of $μ^- N$$ \to$$ μ^- VX$ at high energies and $ν_μN $$\to$$ μ^- VX$ at both high and low energies. We also present the predictions for $ν_μN$$ \to$$ μ^- VX$ at NOMAD energies in the target fragmentation region using a valence quark model.
We present a compact form of the leptonic currents for the computation of the processes involving an initial virtual boson (photon, $W^{\pm}$ or $Z_0$). For deeply inelastic scattering, once the azimuthal angle of the plane expanded by the initial- and final-state leptons are integrated over in the boson-proton rest frame, the azimuthal-asymmetric terms vanish, which, however, is NOT true when some physical quantities (such as the transverse momentum of the observed particle) are specified in laboratory frame. The abuse of the symmetry may lead to wrong results.
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…
In inclusive deep-inelastic lepton-hadron scattering multi-photon exchange between the leptonic and the hadronic part of the process causes single spin asymmetries. The asymmetries exist for a polarized target as well as a polarized incoming or outgoing lepton, if the polarization vector has a component transverse with respect to the reaction plane. The spin dependent parts of the single polarized cross sections are suppressed like $α_{em} m_{pol}/Q$ - where $m_{pol}$ denotes the mass of the polarized particle - compared to the leading terms of the cross section for unpolarized or double-polar…
It is shown that new data from the HERMES collaboration, as well as all of the earlier improved data from experiments concerning the EMC effect and shadowing in deep-inelastic scattering of leptons from nuclei, provide strong evidence for an explicit dynamical role played by exchanged quarks and nuclear gluons in the basic, tightly-bound systems of three and four nucleons, He3 and He4. This opens the way for specific quark-gluon dynamics instigating multinucleon correlations in nuclei.
The processes of lepton-nucleon scattering, including ones with both polarized beams, at high energy provide relevant information about interaction and particles structure, allowing to analyze nucleon spin structure. As energy and experimental accuracy rise, necessity to improve Born cross sections and polarized asymmetries with higher order radiative corrections becomes substantial. In this report we stress on lowest order bremsstrahlung corrections treatment using helicity amplitudes method as applied to actual nowadays charged current lepton-nucleon deep inelastic processes, that allows to …
The reaction e + p ---> photon + jet + X is studied in QCD at the next-to-leading order. Previous studies on inclusive distributions showed a good agreement with ZEUS data. To obtain a finer understanding of the dynamics of the reaction, several correlation functions are evaluated for ZEUS kinematics.
Physics and programming aspects are discussed for a Fortran 77 Monte Carlo program to simulate complete events in deep inelastic lepton-nucleon scattering. The parton level interaction is based on the standard model electroweak cross sections, which are fully implemented in leading order for any lepton of arbitrary polarization, and different parametrizations of parton density functions can be used. First order QCD matrix elements for gluon radiation and boson-gluon fusion are implemented and higher order QCD radiation is treated using parton showers. Hadronization is performed using the Lund …
Inclusive e^\pm p single and double differential cross sections for neutral (NC) and charged current (CC) deep inelastic scattering processes are measured with the H1 detector at HERA. The data were taken at a centre-of-mass energy of \sqrt{s} = 319 GeV with a total integrated luminosity of 327.8 pb^{-1} shared between two lepton beam charges and two longitudinal lepton polarisation modes. The differential cross sections are measured in the range of negative four-momentum transfer squared, Q2, between 60 and 50 000 GeV2, and Bjorken x between 0.0008 and 0.65. The measurements are combined with…
Deep inelastic scattering of leptons off nuclear targets is analized within the convolution model taking into account nucleon-nucleon correlations. We show that in the nuclear medium nucleons are distributed according to a function that exhibits a sizeable Q**2-dependence and reduces to the ordinary light-cone distribution in the Bjorken limit. At Q**2 < 50 (GeV/c)**2 and x > 1 this Q**2-dependence turns out to be stronger than the one associated with the nucleon structure function, predicted by pertubative quantum chromodynamics.
For theoretically consistent determination of $α_s$ from jet rates in deep inelastic scattering the dependence on $α_s$ of parton distribution functions is in principle as important as that of hard scattering cross-sections. For the kinematical region accessible at HERA we investigate in detail numerical importance of these two sources of the $α_s$ dependence of jet rates.
We derive a general framework for describing semi-inclusive deep-inelastic lepton-nucleon scattering in terms of the unintegrated parton distributions and other higher twist parton correlations. Such a framework provides a consistent approach to the calculation of inclusive and semi-inclusive cross sections including higher twist effects. As an example, we calculate the azimuthal asymmetries to the order of 1/Q in semi-inclusive process with transversely polarized target. A non-vanishing single-spin asymmetry in the ``triggered inclusive process'' is predicted to be 1/Q suppressed with a part …
Collider signals of dark photons are an exciting probe for new gauge forces and are characterized by events with boosted lepton jets. Existing techniques are efficient in searching for muonic lepton jets but due to substantial backgrounds have difficulty constraining lepton jets containing only electrons. This is unfortunate since upcoming intensity frontier experiments are sensitive to dark photon masses which only allow electron decays. Analyzing a recently proposed model of kinetic mixing, with new scalar particles decaying into dark photons, we find that existing techniques for electron je…
We present the perturbative prediction for three-jet production cross section in DIS at the NLO accuracy. We study the dependence on the renormalization and factorization scales of exclusive three-jet cross section. The perturbative prediction for the three-jet differential distribution as a function of the momentum transfer is compared to the corresponding data obtained by the H1 collaboration at HERA.
The production of jets in charged-current deep-inelastic scattering (CC DIS) probes simultaneously the strong and the electroweak sectors of the Standard Model; its measurement provides important information on the quark flavour structure of the proton. We compute third-order (N3LO) perturbative QCD corrections to this process, fully differential in the jet and lepton kinematics. We observe a substantial reduction in the theory uncertainty, to sub-percent level throughout the relevant kinematical range, thus enabling precision phenomenology with jet observables.
The main experimental results on jet production at HERA are reviewed. A study of jet shapes shows that the internal structure of jets is well understood. The potential to accurately determine the strong coupling constant using jet rates is discussed. First attempts to extract the gluon density in next-to-leading order are presented. Although fixed order perturbative QCD is able to describe the shape of most variables associated to the hard subprocess leading to jets, it does not reproduce the absolute dijet rate over a large phase space region.
We propose a new sequential jet reconstruction algorithm for future lepton colliders at the energy frontier. The Valencia algorithm combines the natural distance criterion for lepton colliders with the greater robustness against backgrounds of algorithms adapted to hadron colliders. Results on a detailed Monte Carlo simulation of $t\bar{t}$ and $ZZ$ production at future linear $e^+e^-$ colliders (ILC and CLIC) with a realistic level of background overlaid, show that it achieves better performance in the presence of background.
We calculate the polarizations for different octet hyperons produced in the current fragmentation regions of the deeply inelastic lepton-nucleon scatterings $μ^-N \to μ^- HX$ and $ν_μ N \to μ^- HX$ at high energy using different models for spin transfer in fragmentation processes. The results show that measurements of those hyperon polarizations should provide useful information to distinguish between different models in particular the SU(6) and the DIS pictures used frequently in the literature. We found, in particular, that measuring the polarization of $Σ^+$ produced in these processes can …
In deeply inelastic lepton-nucleus scattering (DIS), the average jet transverse momentum is broadened because of the multiple scattering in the nuclear medium. The size of jet broadening is proportional to the multi-parton correlation functions inside nuclei. We show that at leading order, jet broadening in DIS and nulcear enhancement in di-jet momentum imbalance and Drell-Yan $< q_T^2 > $ share the same four-parton correlation functions. We argue that jet broadening in DIS provide an indenpendent measurement of the four-parton correlation functions and a test of QCD treatment of multiple scat…
A complete next-to-leading order QCD calculation of deep inelastic electron-photon scattering including direct and resolved real photon components is presented. Soft and collinear singularities are extracted using the phase space slicing method. Application of the results for the prediction of single- and dijet cross sections at the LEP e+e- collider are presented, using the Snowmass jet definition. The dependence of the cross sections on the transverse momentum and on the rapidities of the jets are discussed.
The production of jets in charged current deep inelastic scattering (CC DIS) constitutes a class of observables that can be used to simultaneously test perturbative predictions for the strong and the electroweak sectors of the Standard Model. We compute both single jet and di-jet production in CC DIS for the first time at next-to-next-to-leading order (NNLO) in the strong coupling. Our computation is fully differential in the jet and lepton kinematics, and we observe a substantial reduction of scale variation uncertainties in the NNLO predictions compared to next-to-leading order (NLO). Our ca…
We study the perturbative QCD corrections to heavy-quark structure functions of charged-lepton deep-inelastic scattering and their impact on global fits of parton distributions. We include the logarithmically enhanced terms near threshold due to soft gluon resummation in the QCD corrections at next-to-next-to-leading order. We demonstrate that this approximation is sufficient to describe the available HERA data in most parts of the kinematic region. The threshold-enhanced next-to-next-to-leading order corrections improve the agreement between predictions based on global fits of the parton dist…
A leading order QCD analysis of spin asymmetries in polarized deep inelastic lepton nucleon scattering is presented within the framework of the radiative parton model. Two resulting sets of plausible leading order spin dependent parton distributions are presented, respecting the fundamental positivity constraints down to the low resolution scale $Q^2=μ_{LO}^2=0.23$ GeV$^2$. The $Q^2$ dependence of the spin asymmetries $A_1^{p,n,d}(x,Q^2)$ is investigated in the range $1 \leq Q^2 \leq 20$ GeV$^2$ and shown to be non-negligible for $x$-values relevant for the analysis of present data and possibl…
The three well-known forms of relativistic dynamics are unitarily equivalent and the problem of constructing the current operators can be solved in any form. However the notion of the impulse approximation is reasonable only in the point form. In particular, the parton model which is the consequence of the impulse approximation in the front form is incompatible with Lorentz invariance, P invariance and T invariance. The results for deep inelastic scattering based on the impulse approximation in the point form give natural qualitative explanation of the fact that the values given by the parton …
The composite model is constructed to describe inelastic high-energy scattering of muons and taus in standard rock. It involves photonuclear interactions at low $Q^2$ as well as moderate $Q^2$ processes and the deep inelastic scattering (DIS). In the DIS region the neutral current contribution is taken into consideration. Approximation formulas both for the muons and tau energy loss in standard rock are presented for wide energy range.
We argue that the production of forward jets in polarised deep inelastic scattering can be a useful tool for probing the double $ln^2(1/x)$ resummation effects which control the polarised deep inelastic scattering for small values of the Bjorken parameter $x$. We solve the corresponding integral equations generating the double $ln^2(1/x)$ resummation and calculate the differential structure function describing the forward jet production in the small $x$ regime which can possibly be probed by the polarised HERA measurements. We show that these structure functions should exhibit the characterist…
We have made a thorough investigation of the nuclear structure function W_2A in the region of 0.8 < x < 1.5 and Q^2 < 20 GeV^2, separating the quasielastic and inelastic plus deep inelastic contributions. The agreement with present experimental data is good giving support to the results for both channels. Predictions are made in yet unexplored regions of x and Q^2 to assert the weight of the quasielastic or inelastic channels. We find that at Q^2 < 4 GeV^2 the structure function is dominated by the quasielastic contributions for x < 1.5, while for values of Q^2 > 15 GeV^2 and the range of x st…
Hadronic jets in deeply inelastic electron-proton collisions are produced by the scattering of a parton from the proton with the virtual gauge boson mediating the interaction. The HERA experiments have performed precision measurements of inclusive single jet production and di-jet production in the Breit frame, which provide important constraints on the strong coupling constant and on parton distributions in the proton. We describe the calculation of the next-to-next-to-leading order (NNLO) QCD corrections to these processes, and assess their size and impact. A detailed comparison with data fro…
