arXiv subjects

J. F. Owens

Publications and source records attributed to J. F. Owens.

At least 37 records · Page 2Linked to original sources

arXiv2011

Uncertainties in determining parton distributions at large x

We critically examine uncertainties in parton distribution functions (PDFs) at large x arising from nuclear effects in deuterium F2 structure function data. Within a global PDF analysis, we assess the impact on the PDFs from uncertainties in the deuteron wave function at short distances and nucleon off-shell effects, the use of relativistic kinematics, as well as the use of less a restrictive parametrization of the d/u ratio. We find that in particular the d-quark and gluon PDFs vary significantly with the choice of nuclear model. We highlight the impact of these uncertainties on the determination of the neutron structure function, and on W boson production and parton luminosity at the Tevatron and the LHC. Finally, we discuss prospects for new measurements sensitive to the d-quark and gluon distributions but insensitive to nuclear corrections.

hep-ph↗

arXiv2011

Nuclear corrections in neutrino-nucleus DIS and their compatibility with global NPDF analyses

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. We find that it is not possible to accommodate the data from nu-A and l^+A DIS by an acceptable combined fit. Our result has strong implications for the extraction of both nuclear and proton parton distribution functions using combined neutrino and charged-lepton data sets.

hep-ph↗

arXiv2011

Probing gluon and heavy-quark nuclear PDFs with photon + heavy quark production in pA collisions

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 γ+ 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. Thus, the nuclear production ratio R^{γ+Q}_{pA} can provide strong constraints, over a broad x-range, on the poorly determined nuclear parton distribution functions which are extremely important for the interpretation of results in heavy-ion collisions.

hep-ph↗

arXiv2010

PDF Nuclear Corrections for Charged Lepton and Neutrino Deep Inelastic Scattering Processes

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.

hep-ph↗

arXiv2010

New parton distributions from large-x and low-Q^2 data

We report results of a new global next-to-leading order fit of parton distribution functions in which cuts on W and Q are relaxed, thereby including more data at high values of x. Effects of target mass corrections (TMCs), higher twist contributions, and nuclear corrections for deuterium data are significant in the large-x region. The leading twist parton distributions are found to be stable to TMC model variations as long as higher twist contributions are also included. The behavior of the d quark as x-->1 is particularly sensitive to the deuterium corrections, and using realistic nuclear smearing models the d-quark distribution at large x is found to be softer than in previous fits performed with more restrictive cuts.

hep-ph↗

arXiv2009

Terascale Physics Opportunities at a High Statistics, High Energy Neutrino Scattering Experiment: NuSOnG

This article presents the physics case for a new high-energy, ultra-high statistics neutrino scattering experiment, NuSOnG (Neutrino Scattering on Glass). This experiment uses a Tevatron-based neutrino beam to obtain over an order of magnitude higher statistics than presently available for the purely weak processes $ν_μ+e^- \to ν_μ+ e^-$ and $ν_μ+ e^- \to ν_e + μ^-$. A sample of Deep Inelastic Scattering events which is over two orders of magnitude larger than past samples will also be obtained. As a result, NuSOnG will be unique among present and planned experiments for its ability to probe neutrino couplings to Beyond the Standard Model physics. Many Beyond Standard Model theories physics predict a rich hierarchy of TeV-scale new states that can correct neutrino cross-sections, through modifications of $Zνν$ couplings, tree-level exchanges of new particles such as $Z^\prime$s, or through loop-level oblique corrections to gauge boson propagators. These corrections are generic in theories of extra dimensions, extended gauge symmetries, supersymmetry, and more. The sensitivity of NuSOnG to this new physics extends beyond 5 TeV mass scales. This article reviews these physics opportunities.

hep-ph↗

arXiv2009

Gamma-Jet Tomography of Quark-Gluon Plasma in High-Energy Nuclear Collisions

Within the next-to-leading order (NLO) perturbative QCD (pQCD) parton model, suppression of away-side hadron spectra associated with a high $p_{T}$ photon due to parton energy loss is shown to provide a complete tomographic picture of the dense matter formed in high-energy heavy-ion collisions at RHIC. Dictated by the shape of the $γ$-triggered jet spectrum in NLO pQCD, hadron spectra at large $z_T=p_T^{h}/p_T^γ \stackrel{>}{\sim} 1$ are more susceptible to parton energy loss and therefore are dominated by surface emission of $γ$-triggered jets, whereas small $z_{T}$ hadrons mainly come from fragmentation of jets with reduced energy from volume emission. These lead to different centrality dependence of the hadron suppression in different regions of $z_{T}$.

hep-ph↗

arXiv2009

Expression of Interest for Neutrinos Scattering on Glass: NuSOnG

We propose a 3500 ton (3000 ton fiducial volume) SiO_2 neutrino detector with sampling calorimetry, charged particle tracking, and muon spectrometers to run in a Tevatron Fixed Target Program. Improvements to the Fermilab accelerator complex should allow substantial increases in the neutrino flux over the previous NuTeV quad triplet beamline. With 4E19 protons on target/year, a 5 year run would achieve event statistics more than 100 times higher than NuTeV. With 100 times the statistics of previous high energy neutrino experiments, the purely weak processes [ν_μ e^- \to ν_μ+ e^-] and [ν_μ e^- \to ν_e + μ^-] (inverse muon decay) can be measured with high accuracy for the first time. The inverse muon decay process is independent of strong interaction effects and can be used to significantly improve the flux normalization for all other processes. The high neutrino and antineutrino fluxes also make new searches for lepton flavor violation and neutral heavy leptons possible. In this document, we give a first look at the physics opportunities, detector and beam design, and calibration procedures.

hep-ex↗

arXiv2009

QCD Precision Measurements and Structure Function Extraction at a High Statistics, High Energy Neutrino Scattering Experiment: NuSOnG

We extend the physics case for a new high-energy, ultra-high statistics neutrino scattering experiment, NuSOnG (Neutrino Scattering On Glass) to address a variety of issues including precision QCD measurements, extraction of structure functions, and the derived Parton Distribution Functions (PDFs). This experiment uses a Tevatron-based neutrino beam to obtain a sample of Deep Inelastic Scattering (DIS) events which is over two orders of magnitude larger than past samples. We outline an innovative method for fitting the structure functions using a parameterized energy shift which yields reduced systematic uncertainties. High statistics measurements, in combination with improved systematics, will enable NuSOnG to perform discerning tests of fundamental Standard Model parameters as we search for deviations which may hint of "Beyond the Standard Model" physics.

hep-ex↗

arXiv2009

Tomography of high-energy nuclear collisions with photon-hadron correlations

Within the next-to-leading order (NLO) perturbative QCD (pQCD) parton model, suppression of away-side hadron spectra associated with a high $p_{T}$ photon due to parton energy loss is studied in high-energy heavy-ion collisions. Dictated by the shape of the $γ$-associated jet spectrum in NLO pQCD, hadron spectra at large $z_T=p_T^{h}/p_T^γ \stackrel{>}{\sim} 1$ are more sensitive to parton energy loss and therefore are dominated by surface emission of $γ$-associated jets, whereas small $z_{T}$ hadrons mainly come from fragmentation of jets with reduced energy which is controlled by the volume emission. These lead to different centrality dependence of the $γ$-hadron suppression for different values of $z_{T}$. Therefore, a complete measurement of the suppression of $γ$-triggered hadron spectra, including its dependence on the orientation of the $γ$-hadron pair with respect to the reaction plane, allows the extraction of the spatial distribution of jet quenching parameters, achieving a true tomographic study of the quark-gluon plasma in high-energy heavy-ion collisions.

nucl-th↗

arXiv2009

Direct Photon Production in Association With A Heavy Quark At Hadron Colliders

Results of a next-to-leading order calculation of the inclusive cross section for a photon and a heavy quark (charm or bottom), $p \bar p / pp \to γ+Q +X$, are presented. Pointlike photon subprocesses through ${\cal O}(αα_{s}^2)$ and fragmentation subprocesses through ${\cal O}(α_{s}^3)$ are included. The calculation is performed using a phase space slicing technique so that the effects of experimental cuts can be included. Results for the ratios of the charm and bottom cross sections are presented and the systematics of the various subprocesses for both the Tevatron and the LHC are compared and contrasted.

hep-ph↗

arXiv2008

Nuclear Parton Distribution Functions

We study nuclear effects of charged current deep inelastic neutrino-iron scattering in the framework of a chi^2 analysis of parton distribution functions (PDFs). We extract a set of iron PDFs which are used to compute x_Bj-dependent and Q^2-dependent nuclear correction factors for iron structure functions which are required in global analyses of free nucleon PDFs. We compare our results with nuclear correction factors from neutrino-nucleus scattering models and correction factors for charged-lepton--iron scattering. We find that, except for very high x_Bj, our correction factors differ in both shape and magnitude from the correction factors of the models and charged-lepton scattering.

hep-ph↗

arXiv2008

Parton distribution function uncertainties & nuclear corrections for the LHC

We study nuclear effects of charged current deep inelastic neutrino-iron scattering in the framework of a chi^2 analysis of parton distribution functions (PDFs). We extract a set of iron PDFs which are used to compute x_Bj-dependent and Q^2-dependent nuclear correction factors for iron structure functions which are required in global analyses of free nucleon PDFs. We compare our results with nuclear correction factors from neutrino-nucleus scattering models and correction factors for charged lepton-iron scattering. We find that, except for very high x_Bj, our correction factors differ in both shape and magnitude from the correction factors of the models and charged-lepton scattering.

hep-ph↗

arXiv2008

A NLO analysis on fragility of dihadron tomography in high energy $AA$ collisions

The dihadron spectra in high energy $AA$ collisions are studied within the NLO pQCD parton model with jet quenching taken into account. The high $p_T$ dihadron spectra are found to be contributed not only by jet pairs close and tangential to the surface of the dense matter but also by punching-through jets survived at the center while the single hadron high $p_T$ spectra are only dominated by surface emission. Consequently, the suppression factor of such high-$p_T$ hadron pairs is found to be more sensitive to the initial gluon density than the single hadron suppression factor.

hep-ph↗

arXiv2008

Punch-through jets in $A+A$ collisions at RHIC/LHC

High $p_T$ single and dihadron production is studied within a NLO pQCD parton model with jet quenching in high energy $A+A$ collisions at the RHIC/LHC energy. A simultaneous $χ^2$-fit to both single and dihadron spectra can be achieved within a narrow range of energy loss parameter. Punch-through jets are found to result in the dihadron suppression factor slightly more sensitive to medium than the single hadron suppression factor at RHIC. Such jets at LHC are found to dominate high $p_T$ dihadron production and the resulting dihadron spectra are more sensitive to the initial parton distribution functions than the single hadron spectra.

hep-ph↗

arXiv2008

Nuclear PDFs from neutrino deep inelastic scattering

We study nuclear effects in charged current deep inelastic neutrino-iron scattering in the frame-work of a chi^2 analysis of parton distribution functions. We extract a set of iron PDFs and show that under reasonable assumptions it is possible to constrain the valence, light sea and strange quark distributions. Our iron PDFs are used to compute x_{Bj}-dependent and Q^2-dependent nuclear correction factors for iron structure functions which are required in global analyses of free nucleon PDFs. We compare our results with nuclear correction factors from neutrino-nucleus scattering models and correction factors for charged lepton-iron scattering. We find that, except for very high x_{Bj}, our correction factors differ in both shape and magnitude from the correction factors of the models and charged-lepton scattering.

hep-ph↗

arXiv2007

Dihadron Tomography of High-Energy Nuclear Collisions in NLO pQCD

Back-to-back dihadron spectra in high-energy heavy-ion collisions are studied within the next-to-leading order (NLO) perturbative QCD parton model with jet quenching incorporated via modified jet fragmentation functions due to radiative parton energy loss in dense medium. The experimentally observed appearance of back-to-back dihadrons at high $p_T$ is found to originate mainly from jet pairs produced close and tangential to the surface of the dense matter. However, a substantial fraction of observed high $p_T$ dihadrons also comes from jets produced at the center of the medium after losing finite amount of energy. Consequently, the suppression factor of such high-$p_T$ hadron pairs is found to be more sensitive to the initial gluon density than the single hadron spectra that are dominated by surface emission. A simultaneous $χ^2$-fit to both the single and dihadron spectra can be achieved within a narrow range of the energy loss parameters $ε_0=1.6-2.1$ GeV/fm. Because of the flattening of the initial jet production spectra, high $p_T$ dihadrons at the LHC energy are found to be more robust as probes of the dense medium.

nucl-th↗

arXiv2007

The impact of new neutrino DIS and Drell-Yan data on large-x parton distributions

New data sets have recently become available for neutrino and antineutrino deep inelastic scattering on nuclear targets and for inclusive dimuon production in pp pd interactions. These data sets are sensitive to different combinations of parton distribution functions in the large-x region and, therefore, provide different constraints when incorporated into global parton distribution function fits. We compare and contrast the effects of these new data on parton distribution fits, with special emphasis on the effects at large x. The effects of the use of nuclear targets in the neutrino and antineutrino data sets are also investigated.

hep-ph↗