### Conveners

#### WG2: Small-x, Diffraction and Vector Mesons

- Mario Deile (CERN)
- Stephane Munier (Ecole polytechnique)
- Lidia Maria Gorlich (Polish Academy of Sciences (PL))

#### WG2: Small-x, Diffraction and Vector Mesons

- Stephane Munier (Ecole polytechnique)
- Mario Deile (CERN)
- Lidia Maria Gorlich (Polish Academy of Sciences (PL))

#### WG2: Small-x, Diffraction and Vector Mesons

- Mario Deile (CERN)
- Stephane Munier (Ecole polytechnique)
- Lidia Maria Gorlich (Polish Academy of Sciences (PL))

#### WG2: Small-x, Diffraction and Vector Mesons

- Lidia Maria Gorlich (Polish Academy of Sciences (PL))
- Mario Deile (CERN)
- Stephane Munier (Ecole polytechnique)

Janusz Malka
(DESY)

29/04/2014, 08:50

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

Data in which a proton is tagged along the beampipe after the primary
interaction represents the cleanest way to measure diffraction. Data from
both H1 and ZEUS collaborations on inclusive diffractive deep inelastic
scattering, with a tagged proton, have been combined. Inclusive
diffractive deep inelastic scattering can be considered as the exchange of
a colourless object and is...

Adrien Besse
(IRFU/SPhN CEA)

29/04/2014, 09:20

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

Many progress have been made in recent years in the field of exclusive electroproduction of mesons. I will describe different theoretical descriptions of this family of processes within the frameworks of kt- factorization, collinear factorization or modified perturbative approach. We systematically compare theoretical expectations to existing data and discuss the impact of QCD evolution...

Amir Rezaeian
(Universidad Tecnica Federico Santa Maria)

29/04/2014, 09:50

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

We confront the Impact-Parameter dependent Color Glass Condensate dipole (b-CGC) model to the recently released high precision combined HERA data and obtain its parameters. The b-CGC results are then compared to data at small-x for the structure function, the longitudinal structure function, the charm structure function, exclusive vector meson (J/\psi, \phi, \rho) production and Deeply Virtual...

Mr
Radek Zlebcik
(Charles University (CZ))

29/04/2014, 10:10

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

The cross section of diffractive process ep$\to$eXp is presented where
the system X contains at least two jets and the leading final state
proton is tagged in the H1 Very Forward Proton Spectrometer
(VFPS). The measurement is performed for untagged photoproduction with
Q$^{2}$ < 2 GeV$^{2}$ in photon virtuality and for deep-inelastic-scattering
with 4 GeV$^{2}$ < Q$^{2}$ < 80 GeV$^{2}$....

Marcin Guzik

29/04/2014, 11:00

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

The exclusive production of dijets in diffractive deep inelastic lepton-proton scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 372 pb$^{-1}$ of $e^\pm p$ data. The measurement has been performed in the kinematic range $Q^2 > 25\,\mathrm{GeV}^2$, $90 < W < 250\,\mathrm{GeV}$ and $x_{\rm I\!P} < 0.01$, where $Q^2$ is the virtuality of exchanged...

Boris Pokorny
(Charles University Prague)

29/04/2014, 11:20

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

In this measurement, the cross section for dijet production in
diffractive deep-inelastic scattering is presented. The diffractive
events are selected by requiring the presence of a Large Rapidity Gap
in the forward region of H1 detector. The data have been collected
during the HERA-2 period and correspond to an integrated luminosity of
284 pb$^{-1}$. The data cover the range x_P <0.03...

Sergey Levonian
(Deutsches Elektronen-Synchrotron (DE))

29/04/2014, 11:40

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

The first measurement of exclusive photoproduction of rho meson
associated with the leading neutron at HERA is presented.
The data are taken with the H1 detector in the years 2006-2007
and correspond to an integrated luminosity of 1.16 pb-1.
The rho mesons are reconstructed from decay pions in the central
tracking chamber, while the leading neutrons, carrying a large
fraction of the...

Prof.
Goulianos Konstantin
(The Rockefeller University)

29/04/2014, 14:00

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

Predictions of diffractive proton-proton cross sections at LHC, and of the total and total-inelastic proton-proton cross sections based on the RENORM unitarization model, also known as the MBR (minimum-bias-Rockefeller) model implemented in PYTHIA8-MBR, are confirmed by recent LHC measurements. Several other available diffraction models are discussed, highlighting differences among them and...

Dr
Mario Deile
(CERN)

29/04/2014, 14:30

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

The TOTEM experiment at the LHC has measured the elastic proton-proton cross-section at sqrt(s) = 7 TeV and 8 TeV in a large range of the four-momentum transfer t. At 8 TeV the measurement reaches into the Coulomb-Nuclear Interference region, providing insight into the nuclear scattering phase and its functional dependence on t.
Via the optical theorem, the measurement of low-|t| elastic...

Valery Khoze
(University of Durham (GB))

29/04/2014, 15:00

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

Central exclusive production (CEP) processes in high-energy proton-(anti)proton collisions offer a very promising framework within which to study both novel aspects of QCD and new physics signals. We discuss the charmonium production applying the Durham pQCD-based model for evaluation of the rates and proton momentum correlations at the Tevatron and LHC energies and compare the results with...

Dr
Marta Ruspa
(Universita e INFN (IT))

29/04/2014, 15:30

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

We present updated measurements of soft single- and double-diffractive cross sections, and of forward rapidity gap cross section, as well as the measurement of the fraction of events with a forward rapidity gap and a jet produced at central rapidity at 7 TeV at the LHC. We compare the results to other measurements and to theoretical predictions implemented in various Monte Carlo...

Valentina Avati
(CERN)

29/04/2014, 16:30

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

After the first LHC Long Shutdown, TOTEM and CMS will join forces to create a combined apparatus with the largest rapidity coverage and with a very performing two-arm proton spectrometer. Focussing on the process of central diffraction opens unique opportunities
for exploring QCD in new phase space regions, for performing competitive electroweak measurements, and for the search for new...

Rafal Staszewski
(IFJ PAN Cracow (PL))

29/04/2014, 16:55

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

The “ATLAS Forward Proton (AFP) detectors” is a project of upgrading
the ATLAS experiment with additional detectors allowing measurements
of the forward protons scattered diffractively or electromagnetically.
A general overview of the AFP detector system and its capabilities
will be given. The AFP physics programme will be discussed, including
soft diffraction, hard inclusive diffraction,...

Marco Adinolfi
(University of Bristol (GB))

29/04/2014, 17:20

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

Studies of quarkonia production in the forward region provide important tests of NRQCD. The LHCb experiment has collected a dataset corresponding to an integrated luminosity of about 3 fb-l in proton-proton collisions at sqrt(s)= 2.76, 7 and 8 TeV. We present studies of the production and polarisation of the J/psi, psi(2S) and chi_c charmonium states as well as those of Upsilon and chi_b...

Tomasz Szumlak
(AGH University of Science and Technology (PL))

29/04/2014, 17:50

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

An updated measurement of exclusive J/psi and psi(2S) vector meson production using 1/fb at 7 TeV is presented. The measured integrated and differential cross-sections are compared to several theoretical predictions. The data are sufficiently sensitive to distinguish between LO and 'NLO' predictions. The forward reach of the LHCb detector probes small values of x, and these results can be...

Lucie De Nooij
(NIKHEF (NL))

29/04/2014, 18:10

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

A measurement of the differential production cross section of the φ(1020)-meson at sqrt(s)=7 TeV using pp collision data collected with the ATLAS experiment is presented.
The φ(1020)-meson selection is based on the identification of kaons by their energy loss in the pixel detector. The differential cross section is measured as a function of the transverse momentum and rapidity. The...

Piotr Kotko

30/04/2014, 14:00

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

We present results for forward jet production in p-p and p-Pb collisions at LHC within
the High Energy Factorization (HEF) framework, obtained using new Monte Carlo programs. The HEF framework incorporates a convolution of unintegrated gluon
densities and off-shell matrix elements. We briefly discuss both components: the relevant evolution
equations and methods to obtain tree level...

Pedro Miguel Ribeiro Cipriano
(Deutsches Elektronen-Synchrotron (DE))

30/04/2014, 14:20

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

The azimuthal correlation between forward and central jets is measured in proton–proton collisions at the LHC, at the centre-of-mass energy of 7 TeV. The forward jet is reconstructed in the hadronic forward (HF) calorimeter in the pseudorapidity region 3.2 < |η| < 4.7, while the central jet is limited to |η| < 2.8. At least one central jet and one forward jet are required to have transverse...

Samantha Katherine Dooling
(Deutsches Elektronen-Synchrotron (DE))

30/04/2014, 14:40

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

Measurements of the differential Drell-Yan and associated jet cross section as a function of the Drell-Yan mass are presented using an integrated luminosity of 4.9 fb-1 in the dimuon channel of proton-proton collision data recorded with the CMS detector at the LHC at sqrt s =7 TeV. Cross sections as a function of the Drell-Yan transverse momentum are measured differentially in the Drell-Yan...

Albert Knutsson
(University of Antwerp (BE))

30/04/2014, 15:00

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

The production yields of leading charged-particle jets and tracks in proton-proton collisions are measured at sqrt(s) = 8 TeV based with the CMS detector. The charged-particle jets (tracks) are measured in the pseudorapidity range |eta| < 1.9 (2.4) for transverse momenta pT > 1 (0.8)GeV. The yield distribution integrated over a given minimum transverse momentum pTmin, falls steeply with...

Dr
Krzysztof Kutak
(IFJ PAN)

30/04/2014, 15:20

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

The recent proposal for an evolution equation for unintegrated gluon densities for large values of the QCD coupling constant α¯s is going to be presented. The approach is based on the linear resummation model introduced by Sta\'{s}to. It is generalized to account for nonlinearity in the diffusive regime. The validity of the diffusive evolution at strong coupling is supported by the AdS/CFT...

Marko Djuric

30/04/2014, 15:40

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

We show how scattering at small-x can be studied by Pomeron exchange in AdS space using the gauge/gravity duality, with good results. In this approach the Pomeron at strong coupling is the graviton Regge trajectory. We use AdS space with a hard wall to mimic confinement effects. We use our results to fit HERA data, most recently for vector meson production, where both the proton and vector...

Guillaume Beuf
(University of Santiago de Compostela)

30/04/2014, 16:30

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

High-energy evolution equations like BFKL, BK or JIMWLK are derived formally at
infinite energy. In order to use those equations to resum leading logs in a physical observable at any finite energy in a consistent way, one needs to modifiy these equations by a kinematical constraint.
I will discuss this issue in general, and show how to address the additional complications arising in...

Yair Mulian

30/04/2014, 17:00

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

The rapidity (energy) evolution of hadronic observables in scattering of a dilute perturbative projectile on a dense gluonic target is described in QCD by the JIMWLK equation. This is a functional non-linear equation that is consistent with the QCD unitarity. JIMWLK reduces to the linear BFKL equation when the scattering probability is low.
I'll first sketch the way the leading order JIMWLK...

Tolga Altinoluk
(Universidade de Santiago de Compostela)

30/04/2014, 17:20

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

In the high energy limit, scattering processes can be described within the eikonal approximation, neglecting contributions which are power-suppressed at high energy. In the case of processes involving a large nuclear target, like pA or AA collisions, the Color Glass Condensate effective theory (CGC) is one of the most convenient formalisms based on the eikonal approximation. However, at LHC...

Dr
Leszek Motyka
(Jagiellonian University)

30/04/2014, 17:40

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

Prompt J/psi hadroduction is analyzed beyond the leading twist two-gluon production mechanism. A contribution to the process is sudied in detail in which the meson production is mediated by three-gluon partonic state, with two gluons coming from the target and one gluon from the projectile. This contribution enters at non-leading twist, but is enhanced at large energies due to large double...

Michal Deak
(Universidade de Santiago de Compostela)

30/04/2014, 18:00

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

We present the calculation of the finite part of the heavy quark impact factor at next-to-leading logarithmic accuracy in a form suitable for phenomenological studies at the LHC within the $k_T$-factorization scheme as described in the publication JHEP 1312 (2013) 066.

Marco Adinolfi
(University of Bristol (GB))

01/05/2014, 08:50

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

The production of Jpsi mesons with rapidity 1.5 < y < 4.0 or −5.0 < y < −2.5 and transverse momentum pT<14GeV/c is studied with the LHCb detector in proton-lead collisions at a proton-nucleon centre-of-mass energy s_NN= Sqrt 5TeV. The analysis is based on a data sample corresponding to an integrated luminosity of about 1.6nb−1. For the first time the nuclear modification factor and...

Heikki Mäntysaari
(University of Jyväskylä)

01/05/2014, 09:10

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

The Color Class Condensate offers a consistent framework to describe
high-energy (small-x) data from various experiments. The
non-perturbative input for these calculations, the dipole-target
amplitude at initial Bjorken-x, can be obtained by performing a fit to
electron-proton deep inelastic scattering data.
We determine the initial condition for the small-x evolution equation...

Heikki Mäntysaari
(University of Jyväskylä)

01/05/2014, 09:30

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

Deep inelastic scattering is a powerful tool to
study the structure of hadrons and test our understanding of the strong
interaction. The precise proton structure
function measurements done at HERA have been a crucial test for
the Color Glass Condensate effective field
theory description of the high energy hadronic interactions.
Ideally one would want to continue the analysis with...

Orlando Villalobos Baillie
(University of Birmingham (GB))

01/05/2014, 09:50

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

Ultra-Peripheral production of vector mesons investigates those collisions where the impact parameter is larger than the sum of the radii of the two projectiles, implying that electromagnetic processes become dominant. For heavier vector mesons, they can provide a promising way to investigate nuclear shadowing (Pb-Pb) and the gluon structure function (p-Pb). The latest results from this...

Dr
Anna Cisek
(University of Rzeszow)

01/05/2014, 11:00

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

We present results based on our new paper [1]. The amplitude for $\gamma p \to V p$ is calculated
in a pQCD $k_{T}$-factorization approach. The coresponding total cross section for different
unintegrated gluon distributions is calculated and compared with new HERA data for photon-proton collisions.
We also compare the total cross section for $\gamma p \to V p$ reaction with recent data...

Wolfgang Schaefer
(Institute of Nuclear Physics PAN)

01/05/2014, 11:20

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

We report a study on the description of two-photon production of dimuons in proton-proton collisions. We focus on the region of high transverse momentum of the muon pairs, where contributions from proton dissociative events are important.
Here one must go beyond the Weizsaecker-Williams approximation of collinear photons and take the photon transverse momenta into account. The resulting...

Antoni Szczurek
(Institute of Nuclear Physics)

01/05/2014, 11:40

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

We calculate distribution of Higgs boson in rapidity and transverse
momentum within $k_t$-factorization with different unintegrated
gluon distribution functions from the literature (Kimber-Martin-Ryskin,
Jung-Salam, Kutak-Stasto, Kwiecinski CCFM, Ivanov-Nikolaev)
with leading order and next-to-leading order precision and with off-shell
matrix elements.
Special attention is devoted to...

Henri Paul Kowalski
(Deutsches Elektronen Synchrotron (DESY))

01/05/2014, 12:00

WG2: Small-x, Diffraction and Vector Mesons

Oral presentation

We analyse, within a dipole model, the inclusive DIS cross section data, obtained from the combination of the H1 and ZEUS HERA measurements. We show that these high precision data are very well described within the dipole model framework, which is complemented with a valence quark structure functions. We discuss the properties of
the gluon density obtained in this way.