I. Schienbein - Dortmund University

I. Schienbein
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Name
I. Schienbein
Affiliation
Dortmund University
City
Dortmund
Country
Germany

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High Energy Physics - Phenomenology (49)
 
High Energy Physics - Experiment (21)
 
Nuclear Theory (10)
 
Nuclear Experiment (10)

Publications Authored By I. Schienbein

We compare predictions of nCTEQ15 nuclear parton distribution functions with proton-lead vector boson production data from the LHC. We select data sets that are most sensitive to nuclear PDFs and have potential to constrain them. We identify the kinematic regions and flavours where these data can bring new information and will have largest impact on the nuclear PDFs. Read More

We discuss the potential of AFTER@LHC to measure single-transverse-spin asymmetries in open-charm and bottomonium production. With a HERMES-like hydrogen polarised target, such measurements over a year can reach precisions close to the per cent level. This is particularly remarkable since these analyses can probably not be carried out anywhere else Read More

We provide a comprehensive comparison of W/Z vector boson production data in proton-lead and lead-lead collisions at the LHC with predictions obtained using the nCTEQ15 PDFs. We identify the measurements which have the largest potential impact on the PDFs, and estimate the effect of including these data using a Monte Carlo reweighting method. We find this data set can provide information about both the nuclear corrections and the heavy flavor (strange) PDF components. Read More

Renormalization group equations are an essential tool for the description of theories accross different energy scales. Even though their expressions at two-loop for an arbitrary gauge field theory have been known for more than thirty years, deriving the full set of equations for a given model by hand is very challenging and prone to errors. To tackle this issue, we have introduced in [1] a Python tool called PyR@TE; Python Renormalization group equations @ Two-loop for Everyone. Read More

We review a number of ideas put forward in favour of the use of a polarised target along with the proposed idea of a fixed-target experiment using the LHC beams -- AFTER@LHC. A number of recent studies have shown that single transverse-spin asymmetries (STSAs) are large enough to be precisely measured in the region accessible with AFTER@LHC, in particular as regards the Drell-Yan process as well as single-pion, isolated-photon and jet production. AFTER@LHC with a polarised target would also be the ideal experimental set-up to measure the gluon Sivers effect via a number of original quarkonium STSA studies. Read More

Searches for new physics will increasingly depend on identifying deviations from precision Standard Model (SM) predictions. Quantum Chromodynamics (QCD) will necessarily play a central role in this endeavor as it provides the framework for the parton model. However, as we move to higher orders and into extreme kinematic regions, we begin to see the full complexities of the QCD theory. Read More

We present the calculation of the NLO QCD corrections to the electroweak production of top-antitop pairs at the CERN LHC in the presence of a new neutral gauge boson. The corrections are implemented in the parton shower Monte Carlo program POWHEG. Standard Model (SM) and new physics interference effects are properly taken into account. Read More

We present the first official release of the nCTEQ nuclear parton distribution functions with errors. The main addition to the previous nCTEQ PDFs is the introduction of PDF uncertainties based on the Hessian method. Another important addition is the inclusion of pion production data from RHIC that give us a handle on constraining the gluon PDF. Read More

We present the new nCTEQ15 set of nuclear parton distribution functions with uncertainties. This fit extends the CTEQ proton PDFs to include the nuclear dependence using data on nuclei all the way up to 208^Pb. The uncertainties are determined using the Hessian method with an optimal rescaling of the eigenvectors to accurately represent the uncertainties for the chosen tolerance criteria. Read More

QCD resummation predictions for the production of new charged ($W'$) and neutral ($Z'$) heavy gauge bosons decaying leptonically are presented. These results are obtained with our resummation code at next-to-leading order and next-to-leading logarithmic (NLO+NLL) accuracy. Our predictions are compared to PYTHIA at leading order (LO) supplemented with parton showers (PS) and FEWZ at NLO and next-to-next-to-leading order (NNLO) for the $p_T$-differential and total cross sections in the Sequential Standard Model (SSM) and general SU(2)$\times$SU(2)$\times$U(1) models. Read More

We demonstrate that to a very good approximation the scale-evolution of the intrinsic heavy quark content of the nucleon is governed by non-singlet evolution equations. This allows us to analyze the intrinsic heavy quark distributions without having to resort to a full-fledged global analysis of parton distribution functions. This freedom is then exploited to model intrinsic bottom distributions which are so far missing in the literature in order to estimate the impact of this non-perturbative contribution to the bottom-quark PDF, and on parton--parton luminosities at the LHC. Read More

This report reviews the study of open heavy-flavour and quarkonium production in high-energy hadronic collisions, as tools to investigate fundamental aspects of Quantum Chromodynamics, from the proton and nucleus structure at high energy to deconfinement and the properties of the Quark-Gluon Plasma. Emphasis is given to the lessons learnt from LHC Run 1 results, which are reviewed in a global picture with the results from SPS and RHIC at lower energies, as well as to the questions to be addressed in the future. The report covers heavy flavour and quarkonium production in proton-proton, proton-nucleus and nucleus-nucleus collisions. Read More

We present a review of the state-of-the-art of our understanding of the intrinsic charm and bottom content of the nucleon. We discuss theoretical calculations, constraints from global analyses, and collider observables sensitive to the intrinsic heavy quark distributions. A particular emphasis is put on the potential of a high-energy and high-luminosity fixed target experiment using the LHC beams (AFTER@LHC) to search for intrinsic charm. Read More

Heavy quark parton distribution functions (PDFs) play an important role in several Standard Model and New Physics processes. Most analyses rely on the assumption that the charm and bottom PDFs are generated perturbatively by gluon splitting and do not involve any non-perturbative degrees of freedom. It is clearly necessary to test this hypothesis with suitable QCD processes. Read More

2015Apr

This paper describes the physics case for a new fixed target facility at CERN SPS. The SHiP (Search for Hidden Particles) experiment is intended to hunt for new physics in the largely unexplored domain of very weakly interacting particles with masses below the Fermi scale, inaccessible to the LHC experiments, and to study tau neutrino physics. The same proton beam setup can be used later to look for decays of tau-leptons with lepton flavour number non-conservation, $\tau\to 3\mu$ and to search for weakly-interacting sub-GeV dark matter candidates. Read More

The impact of recent measurements of heavy-flavour production in deep inelastic $ep$ scattering and in $pp$ collisions on parton distribution functions is studied in a QCD analysis in the fixed-flavour number scheme at next-to-leading order. Differential cross sections of charm- and beauty-hadron production measured by LHCb are used together with inclusive and heavy-flavour production cross sections in deep inelastic scattering at HERA. The heavy-flavour data of the LHCb experiment impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions $x$ of the proton momentum, down to $x \sim 5 \times 10^{-6}$. Read More

We report on the studies of Transverse-Momentum-Dependent distributions (TMDs) at a future fixed-target experiment --AFTER@LHC-- using the $p^+$ or Pb ion LHC beams, which would be the most energetic fixed-target experiment ever performed. AFTER@LHC opens new domains of particle and nuclear physics by complementing collider-mode experiments, in particular those of RHIC and the EIC projects. Both with an extracted beam by a bent crystal or with an internal gas target, the luminosity achieved by AFTER@LHC surpasses that of RHIC by up to 3 orders of magnitude. Read More

We calculate the cross section for the inclusive production of B mesons in pp and ppbar collisions at next-to-leading order in the general-mass variable-flavor-number scheme and show that a suitable choice of factorization scales leads to a smooth transition to the fixed-flavor-number scheme. Our numerical results are in good agreement with data from the Tevatron and LHC experiments at small and at large transverse momenta. Read More

We present theoretical predictions in the framework of the ANP model for single pion production ($\pi^+, \pi^0$) in $\nu_\mu$ and $\bar\nu_\mu$ scattering off mineral oil and plastic. Our results for the total cross sections and flux averaged differential distributions are compared to all available data of the MiniBooNE and MINER$\nu$A experiments. While our predictions slightly undershoot the MiniBooNE data they reproduce the normalization of the MINER$\nu$A data for the kinetic energy distribution. Read More

QCD resummation predictions for the production of charged (W') and neutral (Z') heavy gauge bosons decaying leptonically are presented. The results of our resummation code at next-to-leading order and next-to-leading logarithmic (NLO+NLL) accuracy are compared to Monte Carlo predictions obtained with PYTHIA at leading order (LO) supplemented with parton showers (PS) and FEWZ at NLO and next-to-next-to-leading order (NNLO) for the $p_T$-differential and total cross sections in the Sequential Standard Model (SSM) and general SU(2)xSU(2)xU(1) models. The LO+PS Monte Carlo and NNLO fixed-order predictions are shown to agree approximately with those at NLO+NLL at small and intermediate $p_T$, respectively, and the importance of resummation for total cross sections is shown to increase with the gauge boson mass. Read More

We report on the opportunities for spin physics and Transverse-Momentum Dependent distribution (TMD) studies at a future multi-purpose fixed-target experiment using the proton or lead ion LHC beams extracted by a bent crystal. The LHC multi-TeV beams allow for the most energetic fixed-target experiments ever performed, opening new domains of particle and nuclear physics and complementing that of collider physics, in particular that of RHIC and the EIC projects. The luminosity achievable with AFTER@LHC using typical targets would surpass that of RHIC by more that 3 orders of magnitude in a similar energy region. Read More

We present updated nCTEQ nuclear parton distribution functions with errors including pion production data from RHIC. We compare them with the results of other groups and present selected LHC applications. Read More

The TeV energy region is currently being explored by both the ATLAS and CMS experiments of the Large Hadron Collider and phenomena beyond the Standard Model are extensively searched for. Large fractions of the parameter space of many models have already been excluded, and the ranges covered by the searches will certainly be increased by the upcoming energy and luminosity upgrades. If new physics has to be discovered in the forthcoming years, the ultimate goal of the high-energy physics program will consist of fully characterizing the newly-discovered degrees of freedom in terms of properties such as their masses, spins and couplings. Read More

A wide range of models beyond the Standard Model predict charged and neutral resonances, generically called $W'$- and $Z'$-bosons, respectively. In this paper we study the impact of such resonances on the deep inelastic scattering of ultra-high energy neutrinos as well as on the resonant charged current $\bar\nu_e e^-$ scattering (Glashow resonance). We find that the effects of such resonances can not be observed with the Pierre Auger Observatory or any foreseeable upgrade of it. Read More

We introduce a Hybrid Variable Flavor Number Scheme (H-VFNS) for heavy flavors, which incorporates the advantages of both the traditional Variable Flavor Number Scheme (VFNS) as well as the Fixed Flavor Number Scheme (FFNS). We include an explicit dependence on number of active flavors $N_F$ in both the Parton Distribution Functions (PDFs) and the strong coupling constant $\alpha_{S}$. This results in sets of coexisting PDFs and $\alpha_{S}$ for $N_F=\{3,4,5,6\}$, that are related analytically by the $\overline{\rm MS}$ matching conditions. Read More

The opportunities which are offered by a next generation and multi-purpose fixed-target experiment exploiting the proton and lead LHC beams extracted by a bent crystal are outlined. In particular, such an experiment can greatly complement facilities with lepton beams by unraveling the partonic structure of polarised and unpolarised nucleons and of nuclei, especially at large momentum fractions. Read More

Although the two-loop renormalization group equations for a general gauge field theory have been known for quite some time, deriving them for specific models has often been difficult in practice. This is mainly due to the fact that, albeit straightforward, the involved calculations are quite long, tedious and prone to error. The present work is an attempt to facilitate the practical use of the renormalization group equations in model building. Read More

We outline the opportunities to study with high precision the interface between nuclear and particle physics, which are offered by a next generation and multi-purpose fixed-target experiment exploiting the proton and ion LHC beams extracted by a bent crystal. Read More

We show for the first time preliminary results of nuclear parton distribution function analysis of charged lepton DIS and Drell-Yan data within the CTEQ framework including error PDFs. We compare our error estimates to estimates of different nPDF groups. Read More

We introduce a Hybrid Variable Flavor Number Scheme for heavy flavors, denoted H-VFNS, which incorporates the advantages of both the traditional Variable Flavor Number Scheme (VFNS) as well as the Fixed Flavor Number Scheme (FFNS). By including an explicit $N_F$-dependence in both the Parton Distribution Functions (PDFs) and the strong coupling constant $\alpha_S$, we generate coexisting sets of PDFs and $\alpha_S$ for $N_F=\{3,4,5,6\}$ at any scale $\mu$, that are related analytically by the $\overline{\text{MS}}$ matching conditions. The H-VFNS resums the heavy quark contributions and provides the freedom to choose the optimal $N_F$ for each particular data set. Read More

We investigate the impact of parton distribution functions (PDFs) uncertainties on W/Z production at the LHC, concentrating on the strange quark PDF. Additionally we examine the extent to which precise measurements at the LHC can provide additional information on the proton flavor structure. Read More

We outline the opportunities for spin physics which are offered by a next generation and multi-purpose fixed-target experiment exploiting the proton LHC beam extracted by a bent crystal. In particular, we focus on the study of single transverse spin asymetries with the polarisation of the target. Read More

We argue that the concept of a multi-purpose fixed-target experiment with the proton or lead-ion LHC beams extracted by a bent crystal would offer a number of ground-breaking precision-physics opportunities. The multi-TeV LHC beams will allow for the most energetic fixed-target experiments ever performed. The fixed-target mode has the advantage of allowing for high luminosities, spin measurements with a polarised target, and access over the full backward rapidity domain --uncharted until now-- up to x_F ~ -1. Read More

We report on the spin and diffractive physics at a future multi-purpose fixed-target experiment with proton and lead LHC beams extracted by a bent crystal. The LHC multi-TeV beams allow for the most energetic fixed-target experiments ever performed, opening new domains of particle and nuclear physics and complementing that of collider physics, in particular that of RHIC and the EIC projects. The luminosity achievable with AFTER using typical targets would surpass that of RHIC by more than 3 orders of magnitude. Read More

We present a phenomenological study of the associated production of a prompt photon and a heavy quark jet (charm or bottom) in Pb-Pb collisions at the LHC. This channel allows for estimating the amount of energy loss experienced by the charm and bottom quarks propagating in the dense QCD medium produced in those collisions. Calculations are carried out at next-to-leading order (NLO) accuracy using the BDMPS-Z heavy-quark quenching weights. Read More

We outline the opportunities for ultra-relativistic heavy-ion physics which are offered by a next generation and multi-purpose fixed-target experiment exploiting the proton and ion LHC beams extracted by a bent crystal. Read More

We review theoretical and phenomenological aspects of heavy flavour production as discussed in the heavy flavour working group of the DIS 2012. Recent theoretical progress includes approximate NNLO calculations for heavy quark structure functions in deep inelastic scattering, the extension of the ACOT heavy flavour scheme to jet production, and advances in top physics where the highlight is clearly the first complete NNLO QCD prediction for top pair production in the $q \bar{q}$ annihilation channel. Furthermore, state of the art phenomenological predictions for open charm and bottom, charmonium, and single top and top pair production are discussed in addition to other topics such as the effect of double parton scattering on heavy quark production. Read More

We compute the structure functions F2 and FL in the ACOT scheme for heavy quark production. We use the complete ACOT results to NLO, and make use of the MSbar massless results at NNLO and N3LO to estimate the higher order mass-dependent corrections. We show numerically that the dominant heavy quark mass effects can be taken into account using massless Wilson coefficients together with an appropriate rescaling prescription. Read More

We analyze the properties of the ACOT scheme for heavy quark production and make use of the MS-Bar massless results at NNLO and N3LO for the structure functions F2 and FL in neutral current deep-inelastic scattering to estimate the higher order corrections. The dominant heavy quark mass effects at higher orders can be taken into account using the massless Wilson coefficients together with an appropriate slow-rescaling prescription implementing the phase space constraints. Combining the exact ACOT scheme at NLO with these expressions should provide a good approximation to the full calculation in the ACOT scheme at NNLO and N3LO. Read More

The 2011 Les Houches workshop was the first to confront LHC data. In the two years since the previous workshop there have been significant advances in both soft and hard QCD, particularly in the areas of multi-leg NLO calculations, the inclusion of those NLO calculations into parton shower Monte Carlos, and the tuning of the non-perturbative parameters of those Monte Carlos. These proceedings describe the theoretical advances that have taken place, the impact of the early LHC data, and the areas for future development. Read More

General SU(2)xSU(2)xU(1) models represent a well-motivated intermediate step towards the unification of the Standard Model gauge groups. Based on a recent global analysis of low-energy and LEP constraints of these models, we perform numerical scans of their various signals at the LHC. We show that total cross sections for lepton and third-generation quark pairs, while experimentally easily accessible, provide individually only partial information about the model realized in Nature. Read More

Global analyses of Parton Distribution Functions (PDFs) have provided incisive constraints on the up and down quark components of the proton, but constraining the other flavor degrees of freedom is more challenging. Higher-order theory predictions and new data sets have contributed to recent improvements. Despite these efforts, the strange quark PDF has a sizable uncertainty, particularly in the small x region. Read More

We analyze the properties of the ACOT scheme for heavy quark production and make use of the \MSbar massless results at NNLO and N3LO for the structure functions F2 and FL in neutral current deep-inelastic scattering to estimate the higher order corrections. For this purpose we decouple the heavy quark mass entering the phase space from the one entering the dynamics of the short distance cross section. We show numerically that the phase space mass is generally more important. Read More

We present predictions for the inclusive production of charmed hadrons at the CERN LHC in the general-mass variable-flavor-number scheme at next-to-leading order. Detailed numerical results are compared to data where available, or presented in a way to ease future comparisons with experimental results. We also point out that measurements at large rapidity have the potential to pin down models of intrinsic charm. Read More

We survey some of the recent developments in the extraction and application of heavy quark Parton Distribution Functions (PDFs). We also highlight some of the key HERA measurements which have contributed to these advances. Read More

The neutrino deep inelastic scattering (DIS) data is very interesting for global analyses of proton and nuclear parton distribution functions (PDFs) since they provide crucial information on the strange quark distribution in the proton and allow for a better flavor decompositon of the PDFs. In order to use neutrino DIS data in a global analysis of proton PDFs nuclear effects need to be understood. We study these effects with the help of nuclear PDFs extracted from global analyses of charged-lepton DIS, Drell-Yan and neutrino DIS data at next-to-leading order in QCD. Read More

We calculate the next-to-leading-order cross section for the inclusive production of B mesons in pp collisions in the general-mass variable-flavor-number scheme, an approach which takes into account the finite mass of the b quarks. We use realistic evolved non-perturbative fragmentation functions obtained from fits to e+e- data and compare results for the transverse-momentum and rapidity distributions at a center-of-mass energy of 7 TeV with recent data from the CMS Collaboration. We find good agreement, in particular at large values of pT. Read More

We present a detailed phenomenological study of the associated production of a prompt photon and a heavy-quark jet (charm or bottom) in proton-nucleus (p-A) and nucleus-nucleus (A-A) collisions. The dominant contribution to the cross-section comes from the gluon--heavy-quark (gQ) initiated subprocess, making this process very sensitive to the gluon and the heavy quark nuclear parton densities. We show that the future p-A data to be collected at the LHC should allow one to disentangle the various nPDF sets currently available. Read More

We present a detailed phenomenological study of direct photon production in association with a heavy-quark jet in pA collisions at the Relativistic Heavy Ion Collider (RHIC) and at the Large Hadron Collider (LHC) at next-to-leading order in QCD. The dominant contribution to the cross-section comes from the gluon--heavy-quark (gQ) initiated subprocess, making \gamma + Q production a process very sensitive to both the gluon and the heavy-quark parton distribution functions (PDFs). Additionally, the RHIC and LHC experiments are probing complementary kinematic regions in the momentum fraction x_2 carried by the target partons. Read More

We perform a global chi^2-analysis of nuclear parton distribution functions using data from charged current neutrino-nucleus deep-inelastic scattering (DIS), charged-lepton-nucleus DIS, and the Drell-Yan (DY) process. We show that the nuclear corrections in nu-A DIS are not compatible with the predictions derived from l^+A DIS and DY data. We quantify this result using a hypothesis-testing criterion based on the chi^2 distribution which we apply to the total chi^2 as well as to the chi^2 of the individual data sets. Read More