### Conveners

#### WG1 Structure Functions and Parton Densities

- Robert Thorne (University College London)
- Ronan McNulty (University College Dublin)
- Katarzyna Wichmann (DESY)

#### WG1 Structure Functions and Parton Densities

- Robert Thorne (University College London)
- Ronan McNulty (University College Dublin)
- Katarzyna Wichmann (DESY)

#### WG1 Structure Functions and Parton Densities

- Ronan McNulty (University College Dublin)
- Robert Thorne (University College London)
- Katarzyna Wichmann (DESY)

#### WG1 Structure Functions and Parton Densities

- Katarzyna Wichmann (DESY)
- Robert Thorne (University College London)
- Ronan McNulty (University College Dublin)

#### WG1 Structure Functions and Parton Densities

- Robert Thorne (University College London)
- Katarzyna Wichmann (DESY)
- Ronan McNulty (University College Dublin)

#### WG1 Structure Functions and Parton Densities

- Robert Thorne (University College London)
- Katarzyna Wichmann (DESY)
- Ronan McNulty (University College Dublin)

#### WG1 Structure Functions and Parton Densities

- Katarzyna Wichmann (DESY)
- Robert Thorne (University College London)
- Ronan McNulty (University College Dublin)

Prof.
Robert Thorne
(University College London)

4/12/16, 9:00 AM

Structure Functions and Parton Densities

We present continuing work on the the MMHT PDFs. We discuss the changes in the PDFs and predictions due to variation in heavy quark masses. We present in detail the impact of the final combined HERA cross section data, and examine the fit quality. We also highlight plans for the future, in particular the potential impact of data sets not included in the current fit, and of new theoretical calculations.

Dr
Juan Rojo
(University of Oxford)

4/12/16, 9:20 AM

Structure Functions and Parton Densities

In this talk we present recent progress in the NNPDF global analysis, in particular work towards an updated NNPDF3.1 release. Recent developments include the inclusion of the combined HERA data and of several new LHC and Tevatron experiments, theoretical improvements such as the FONLL GM-VFN scheme with heavy quark masses, fits with heavy quark mass variations and with intrinsic charm, and...

Prof.
A. Cooper-Sarkar
(Oxford)
, Prof.
Amanda Cooper-Sarkar
(Oxford)
, Prof.
Amanda Cooper-Sarkar
(Oxford University)

4/12/16, 9:40 AM

Structure Functions and Parton Densities

In the HERAPDF2.0 PDF analysis it was noted that the fit $chi^2$
worsens significantly at low $Q^2$ for both NLO and NNLO fits. The
turn over of the reduced cross section at low-$x$ and low $Q^2$ due to
the contribution of the longitudinal cross section $F_L$ is also not
very well described. In this paper the prediction for $F_L$ is
highlighted and the corresponding extraction of $F_2$...

Dr
Agnieszka Luszczak
(Institute of Nuclear Physics)
,
agnieszka luszczak
(Cracow university)

4/12/16, 10:00 AM

Structure Functions and Parton Densities

I analyse, within a dipole model, the inclusive DIS cross section data, obtained from the last HERA measurements (2015). I show that these
high precision data are very well described within the dipole model framework, which is complemented with a valence quark structure functions. I also discuss the role of higher twist corrections to the standard PDFs fit.
This analysis I have done in...

Carl Schmidt
(Michigan State University)

4/12/16, 11:00 AM

Structure Functions and Parton Densities

We discuss recent activities of the CT global analysis group. This includes
an update of CT14 to include the HERA1+2 combined data set, discussion of
CT14 special sets such as CT14QED, intrinsic charm or asymmetric
strange studies, and other current analyses based on CT14.

Sergey Alekhin
(UHH)
, Dr
Sergey Alekhin
(Institute for High Energy Physics (Protvino, Russia))
, Dr
Sergey Alekhin
(Universität Hamburg)
,
Sergey Alekhin
(DESY)

4/12/16, 11:20 AM

Structure Functions and Parton Densities

A new update of the ABM PDFs is presented, which, among other data, includes the new combined HERA DIS data from run II.

Alberto Accardi
(Hampton U. and Jefferson Lab)

4/12/16, 11:40 AM

Structure Functions and Parton Densities

We present a new set of leading twist parton distribution functions, referred to as “CJ15”, which take advantage of developments in the theoretical treatment of nuclear corrections as well as new data. The analysis includes for the first time data on the free neutron structure function from Jefferson Lab and new high-precision charged lepton and W -boson asymmetry data from Fermilab. These...

Dr
Juan Rojo
(University of Oxford)

4/12/16, 12:00 PM

Structure Functions and Parton Densities

We present an updated recommendation for the usage of sets of parton distribution functions at the LHC Run II. We propose a new prescription for the combination of a suitable subset of the available PDF sets, which is presented in terms of a single combined PDF set. We discuss tools which allow for the delivery of this combined set in terms of optimized sets of Hessian eigenvectors or Monte...

Mrs
Ringaile Placakyte
(DESY)

4/12/16, 12:20 PM

Structure Functions and Parton Densities

We review the current status in the determination of parton distribution
functions in view of the precision requirements for LHC in the run II.

Dr
Cynthia Keppel
(Thomas Jefferson National Accelerator Facility)

4/13/16, 9:00 AM

Structure Functions and Parton Densities

Significant progress has recently been made, both experimentally and theoretically, in extracting the neutron structure function from deuterium data. Of particular note are the new CTEQ-JLab (CJ) nuclear corrections for large x PDF extraction, and the Jefferson Lab "BONUS" experiment, where a novel tagged proton spectator approach was employed to isolate the neutron target in electron-deuteron...

Mr
Bryan Ramson
(University of Michigan)

4/13/16, 9:20 AM

Structure Functions and Parton Densities

The Lam-Tung relation, a pertubative QCD, ``Callan-Gross-like'' correlation of the azimuthal and polar angles of leptonic products relative to the initial hadronic plane in multiple frames, defines a standard component of any analysis using Drell-Yan as a nucleon probe. In at least three experiments involving Drell-Yan between various species of pions and nuclei at CERN and Fermilab, the...

Roberto Petti
(University of South Carolina)

4/13/16, 9:40 AM

Structure Functions and Parton Densities

We present a detailed study of nuclear corrections in the deuteron (D) from an analysis of existing data from Deep Inelastic Scattering (DIS) off proton and D, Drell-Yan production in pp and pD interactions, $W^\pm$ and $Z$ boson production in pp and $p \bar p$ collisions. In particular, we discuss the determination of the off-shell correction describing the modification of parton...

Mirko Serino
(Institute of Nuclear Physics, PAN, Cracow)

4/13/16, 10:00 AM

Structure Functions and Parton Densities

Multi parton distribution functions (MPDs) are interesting in view of the study of Multi Parton Interactions in hadron-hadron collisions.
We use the Stirgling-Gaunt sum rules to construct explicitly an initial condition for the double gluon distribution function starting from the known MSTW form of the single gluon distribution function. The result is parameter free. We also consider the...

Markus Konrad Kohler
(Weizmann Institute of Science)

4/13/16, 11:00 AM

Structure Functions and Parton Densities

Photons and weak bosons do not interact strongly with the dense and hot medium formed in the nuclei collisions, thus should be sensitive to the nuclear modification of parton distribution functions (nPDFs). The in-medium modification of heavy Charmonium states plays an important role in studying the hot and dense medium formed in the larger collision systems. The ATLAS detector, optimized for...

Dr
Keppel Cynthia
(Thomas Jefferson National Accelerator Facility)

4/13/16, 11:20 AM

Structure Functions and Parton Densities

World data for the F2 structure function for Iron, as measured by multiple charged lepton and neutrino scattering experiments, are compared. Data obtained from charged lepton and neutrino scattering at larger values of x are in remarkably good agreement with a simple invocation of the 18/5 rule, while a discrepancy in the behavior of the data obtained from the different probes well beyond the...

Aleksander Kusina
(LPSC Grenoble)

4/13/16, 11:40 AM

Structure Functions and Parton Densities

We present the nCTEQ15 global analysis of nuclear parton distribution functions (nPDFs). The main addition to the previous nCTEQ analysis is
the introduction of PDF uncertainties based on a modified Hessian method. Another important improvement is the inclusion of pion production data from RHIC providing additional constraints on gluon PDF. In this presentation we briefly discuss the...

Roberto Petti
(University of South Carolina)
,
Sergey Kulagin
(INR)

4/13/16, 12:00 PM

Structure Functions and Parton Densities

We present the status of our calculation of nuclear parton distribution functions on the basis of our recently developed semi-microscopic model, which takes into account a number of nuclear effects including nuclear shadowing, Fermi motion and nuclear binding, nuclear meson-exchange currents and off-shell corrections to bound nucleon distributions. We discuss in details the dependencies of...

Dr
Ilkka Helenius
(Lund University)

4/13/16, 12:20 PM

Structure Functions and Parton Densities

High-energy nuclear collisions are often classified in terms of centrality. Theoretically the centrality binning is obtained using the Woods-Saxon parametrization for nuclear density as an input for Glauber model. Traditionally the parametrization do not differentiate between protons and neutrons. However, according to measurements in nuclear physics, the density of neutrons decrease slower at...

Dr
Wally Melnitchouk
(Jefferson Lab)

4/13/16, 12:40 PM

Structure Functions and Parton Densities

We examine the efficacy of pion exchange models to simultaneously describe leading neutron electroproduction at HERA and the d-bar - u-bar flavor asymmetry in the proton. A detailed chi^2 analysis of the ZEUS and H1 cross sections, when combined with constraints on the pion flux from Drell-Yan data, allows regions of applicability of one-pion exchange to be delineated. The analysis disfavors...

Dr
Marco Bonvini
(University of Oxford)

4/13/16, 4:30 PM

Structure Functions and Parton Densities

I will discuss the inclusion in PDF fits of two resummations in QCD: threshold (large x) and high-energy (small x). I will present published results for threshold resummation on a global NNPDF, and implication for phenomenology (as well as future plans).
I will then show preliminary results on the effect of resumming small-x logarithms in PDF fits, again in the context of the NNPDF methodology.

Dr
Valerio Bertone
(University of Oxford)

4/13/16, 4:50 PM

Structure Functions and Parton Densities

APFEL is a numerical code specialized for PDF fits that provides a fast
and accurate solution of the DGLAP equations up to NNLO in QCD and LO
in QED. In addition to PDF evolution, APFEL also provides a module
that computes deep-inelastic scattering cross sections in several mass
schemes up to NNLO in QCD. In this contribution I will present the
most recent developments carried out in the...

Mr
Luca Rottoli
(University of Oxford)

4/13/16, 5:10 PM

Structure Functions and Parton Densities

I will discuss the extension of the FONLL variable flavour number scheme to account for a possible intrinsic component of the charm PDF. I will present the results of a PDF fit which includes a fitted charm PDF in the NNPDF framework, and discuss phenomenological implications.

Mr
Oleksandr Zenaiev
(DESY)

4/13/16, 5:30 PM

Structure Functions and Parton Densities

An accurate knowledge of the Parton Distribution Functions (PDF) plays a
critical role for the precision tests of the Standard Model (SM) and impact substantially the theory predictions of Beyond SM high mass production.
We present the xFitter project (former HERAFitter) which provides a unique open-source software framework for the determination of the proton's
PDFs and for the...

Dr
Tie-Jiun Hou
(Southern Methodist University)

4/13/16, 5:50 PM

Structure Functions and Parton Densities

The Parton Distribution Functions(PDFs) are the non-perturbative input of the theoretical calculation of physical observable in a hadron collider. In the era of precision measurement, the uncertainty estimation of the PDFs is sensitive to the searching of new physics. In this talk, the CT14 Monte Carlo replica and its comparison with the CT14 Hessian sets would be presented.

Dr
Emanuele Roberto Nocera
(Rudolf Peierls Centre for Theoretical Physics University of Oxford)

4/13/16, 6:10 PM

Structure Functions and Parton Densities

The behaviour of parton distribution functions (PDFs) at sufficiently small and large values of momentum fractions is expected to be governed by a power law, as a result of Regge theory and spectator counting rules respectively. I investigate in which regions of momentum fraction and energy such an asymptotic behaviour emerges, based on recent determinations of PDFs from a global analysis of...

Aleksandra Lelek
(DESY)

4/14/16, 9:00 AM

Structure Functions and Parton Densities

We describe a new approach to solve the coupled quark and gluon evolution DGLAP evolution equations with a Monte Carlo method. We show that this method is equivalent to other methods. We apply this method to extract quark and gluon parton densities collinear and as transverse momentum dependent (TMD) distributions using the precision HERA DIS data.
The Monte Carlo method for the solution of...

Sara Taheri Monfared
(IPM Istanbul)

4/14/16, 9:25 AM

Structure Functions and Parton Densities

We apply a MC method to solve the evolution equations but use
a gluon density from saturation models as input. The sea and valence quark disributions are obtained from fits to HERA precision data.
We obtain TMD parton distributions (gluon and quarks) satisfying
saturation conditions.

Prof.
Gennady Lykasov
(JINR)

4/14/16, 9:45 AM

Structure Functions and Parton Densities

We study the role of the non-perturbative input to the transverse momentum dependent (TMD)
gluon density in hard processes at the LHC.
We derive the input TMD gluon distribution at a low scale $\mu_0^2 \sim 1$~GeV$^2$
from a fit of inclusive hadron spectra measured at low
transverse momenta in $pp$ collisions at the LHC
and demonstrate that the best description of these spectra
for...

Patrick Connor
(DESY)

4/14/16, 10:05 AM

Structure Functions and Parton Densities

We present the TMDlib project which contains a collection on transverse
momentum dependent (TMD) parton distributions obtained in different
frameworks. The TMDplotter is a a web based plotting tool for TMD parton distributions as well as for collinear parton distributions included in LHAPDF. TMDplotter has additional plotting features, such as parton luminosities for collinear and TMD parton...

Mr
Luca Rottoli
(University of Oxford)

4/14/16, 11:00 AM

Structure Functions and Parton Densities

I will present a state-of-the-art prediction for the prompt atmospheric neutrino flux in the framework of perturbative QCD. The calculation was performed using a gluon PDF constrained at small-x by the inclusion of charm production measurements from the LHCb experiment at 7 TeV, and recently validated with the corresponding 13 TeV data [arXiv:1511.06346, arXiv:1506.08025]

Prof.
Antoni Szczurek
(Institute of Nuclear Physics, Polish Academy of Sciences)

4/14/16, 11:20 AM

Structure Functions and Parton Densities

We investigate different methods to incorporate the effect of
photons in hard processes.
We compare two different approaches used for calculating
cross sections for two-photon $p p \to l^+ l^- X$ process.
In one of the approaches photon is treated as a collinear parton in
the proton. In the second approach recently proposed a $k_t$-factorization
method is used. We discuss how results...

Dr
Fernanda Steffens
(DESY - Zeuthen)

4/14/16, 11:40 AM

Structure Functions and Parton Densities

Although Parton Distribution Functions are the fundamental objects describing the inner structure of hadrons, there exists so far no computation of them from first principles. The most promising candidate for such calculation, lattice QCD, performed successful computations for the masses, charges and form factors but not of the distributions themselves. The reason for this is that quark...

Dr
Stephen Jones
(MPI, Munich)

4/14/16, 12:00 PM

Structure Functions and Parton Densities

We discuss the potential to constrain the small-x PDFs using the exclusive production of heavy vector mesons. The calculation of J/psi and Upsilon photoproduction at NLO in collinear factorisation is described. The different behaviour of the NLO corrections for J/psi and Upsilon is highlighted and we outline what might be expected from the inclusion of these processes in a PDF fit.

Saeedeh Rostami
(Semnan University, Iran)

4/14/16, 12:20 PM

Structure Functions and Parton Densities

Charm quark distribution function play an important role in study of many presses. In the standard global analysis of parton distribution functions, charm quark distribution arises perturbatively by gluon splitting. Nonetheless, existence of a non-perturbative intrinsic charm quark component in the nucleon is predicted by QCD. We present some phenomenological light cone models for...

Mr
Guillermo Gambini
(IFGW-Unicamp)

4/14/16, 12:40 PM

Structure Functions and Parton Densities

We investigate the stability of the saturation regime of the
Gribov-Levin-Ryskin equation against azimuthal perturbations, and argue
that the appearance of unstable modes could lead to the "spontaneus
symmetry breaking" of azimuthal symmetry in high energy pp and AA
collisions. We discuss the phenomenology of this hypothesis in light of
the "harmonic flow" observable seen in heavy ion collisions.