10th International Workshop on Multiple Partonic Interactions at the LHC

Contribution List

65. A tale of Nine Cities and Many Partons: developments in MPI since the first MPI@LHC.

Jonathan Richard Gaunt (CERN), Paolo Bartalini (Central China Normal University CCNU (CN))

10/12/2018, 09:50

Anniversary Talk

We discuss progress in the field of MPI studies over the last ten years, focussing mainly on theoretical developments but also including experimental highlights.

18. Small system physics from CMS: energy and multiplicity dependence of particle correlations

Arthur Moraes (CBPF - Brazilian Center for Physics Research (BR))

10/12/2018, 11:10

WG4

The CMS collaboration presents two talks on small-system physics. This contribution will focus specifically on the dependence of particle correlations on energy and multiplicity

7. Collectivity in small collision systems with ALICE

Katarina Gajdosova (Czech Technical University (CZ))

10/12/2018, 11:40

WG4

Measurements of anisotropic flow provide an important insight into the nature of collectively expanding hot and dense strongly coupled matter in heavy-ion collisions. Over the past years, striking similarities were revealed in numerous experimental results measured in high-multiplicity proton-proton and proton-lead interactions, where no emergence of such a medium was expected.

In this talk,...

13. Low-mass dielectron measurements in high-multiplicity pp collisions with ALICE at the LHC

Ivan Vorobyev (Technische Universitaet Muenchen (DE))

10/12/2018, 12:00

WG4

Electron-positron pairs produced in ultra-relativistic heavy-ion collisions at the LHC carry important information about the system space-time evolution unperturbed by strong final-state interactions. The dielectron continuum is very rich in physics sources: on top of Dalitz and resonance decays of pseudo-scalar and vector mesons, thermal black-body radiation contains the information about the...

32. Modification of inclusive and heavy-flavor jet structures in high-multiplicity pp collisions

Robert Vertesi (Hungarian Academy of Sciences (HU))

10/12/2018, 12:20

WG4

High multiplicity events of small colliding systems at high c.m.s. energies show similar collective features to heavy ion collisions with comparable multiplicities, such as long-range near-side correlations and v_n coefficients [1]. Whether this behaviour may be attributed to the presence of a deconfined state in small systems is an open question. Recent analyses of pp and p-Pb collisions also...

29. Measurements of correlated hadron production with the ATLAS detector

Sarka Todorova (Centre National de la Recherche Scientifique (FR))

10/12/2018, 12:40

WG4

Abstract: We present studies shedding light on the correlated hadron production. This is an important source of information about the early stages of hadron formation and is not yet understood from first principles. In this talk, we will present the measurement of Bose-Einstein correlations using the ATLAS detector along with an analysis of the momentum difference between charged hadrons in...

69. New developments in EPOS

Klaus WERNER

10/12/2018, 15:00

WG2

We report on recent developments concerning the reunification of the two EPOS branches EPOS LHC and EPOS3, essentially concerning the hadronization of the plasma part.

22. LHC tune for hard processes

Paolo Gunnellini (University of Hamburg)

10/12/2018, 15:20

WG2

The LHCEW group on Jets and EW bosons proposes to produce an LHC tune
to provide consistent parameters for the different parton shower and MPI
MC generators. The LHC tune will include data from all LHC collaborations, as well as lower energy data. The parameters to be tuned are those of the UE event and intrinsic kt, but are not connected with the hard process.
The goal is to provide a tune...

50. Rivet for Heavy Ions

Christian Bierlich (Lund University (SE))

10/12/2018, 15:40

WG2

We present new developments in the Rivet framework for comparing theory to experiment, allowing for the first time for easy implementation of – and comparison against – heavy ion data. The framework has notably been extended with tools for centrality estimation and calculation of flow observables, as well as the implementation of several heavy ion analyses. In this talk we will demonstrate...

54. Monte Carlo event generator for double parton interactions in proton nucleus collisions

Mark Strikman (Pennsylvania State University (US))

10/12/2018, 16:00

WG2

We summarize the results of the studies of double parton scattering (DPS) off nuclei in the parton
model [1] and pQCD [2]. A Monte Carlo implementation of the DPS processes is developed which
includes realistic NN correlation in nuclei [3], transverse geometry of hard and soft NN collisions
and distribution over the number of wounded nucleons. This implementation is an extension of the
Monte...

64. Space-time model for colour reconection.

Miroslav Myska (Czech Technical University (CZ))

10/12/2018, 16:20

WG2

The idea behind the space-time colour reconection (CR) is to use the space-time distance between the partons to construct a colour reconnection model. We will describe how the space-time picture is incorporated into Herwig 7 and show the first results of a space-time CR model.

23. Heavy ion and fixed target results at LHCb

Pasquale Di Nezza (INFN e Laboratori Nazionali di Frascati (IT))

10/12/2018, 17:10

WG6

The LHCb experiment pioneered fixed target physics with LHC beams, thanks to the SMOG internal gas target. The forward geometry of the spectrometer are perfectly suitable for a fixed-target programme that, together with ion collisions, enables unique studies that shed light on cosmic ray physics as well as heavy ion physics. We present the first measurement of antiproton production in...

39. Heavy-flavour jet measurements with ALICE

Auro Prasad Mohanty (Utrecht University (NL))

10/12/2018, 17:30

WG6

Heavy quarks are produced in hard scattering processes during the early stages of a heavy-ion collision at ultra-relativistic energies. Their annihilation rate is negligible, and they participate in the whole medium evolution losing their energy via radiative and collisional processes while traversing through the Quark-Gluon Plasma (QGP) formed in such collisions. This allows us to study the...

24. Flow harmonic coefficients in small systems at the LHC: initial or final state effect?

Alba Soto Ontoso (UGR/FIAS)

10/12/2018, 17:50

WG6

The experimental measurements of non-zero flow harmonic coefficients in p+A, and even in p+p, collisions at LHC energies have generated an ample debate on the heavy ion community in the last lustrum. Considered a golden probe of QGP formation in A+A collisions the interpretation of vn’s distinct from zero in small collision systems remains unclear. This is so because a reasonable description...

49. Soft physics from e+e- to AA

Christian Bierlich (Lund University (SE))

10/12/2018, 18:10

WG6

Since the surprising discovery of collective behavior in pp collisions at LHC, hadronization mechanisms has experienced a renewed interest. The prospect that collective behavior in pp and AA collisions might have a common origin, have also prompted efforts to extend MPI models for pp to heavy ion collisions.
In this talk I will outline the efforts of the microscopic model of collectivity...

55. Azimuthal asymmetries on heavy-flavour production from Pb-Pb to pp collisions with ALICE

Davide Caffarri (Nikhef National institute for subatomic physics (NL))

10/12/2018, 18:30

WG6

The heavy-ion physics program at the LHC aims at characterizing the high energy density, high temperature, deconfined partonic state of matter called Quark-Gluon Plasma (QGP).
Azimuthal anisotropies of particles produced in heavy-ion collisions are used to study initial state geometry fluctuations and collective effects that arise from the long-range interactions with non-zero mean free path,...

41. Measurements of two-particle correlations in $e^+e^-$ collisions at 91 GeV with ALEPH archived data

Austin Alan Baty (Massachusetts Inst. of Technology (US))

11/12/2018, 09:00

WG4

This talk summarize the results on two-particle angular correlations for charged particles emitted in $e^+e^−$ collisions data collected at 91 GeV with the ALEPH detector at LEP. With the archived data, the correlation functions are studied over a broad range of pseudorapidity $\eta$ and azimuthal angle $\phi$ with respect to the electron-positron beam axis and the event thrust axis....

11. Studying minijets and MPI with rapidity correlations

Mark Strikman (Penn State University)

11/12/2018, 09:20

WG4

We propose and carry a detailed study of an observable sensitive to different mechanisms of minijet production. The class of observables measures how the transverse momenta of hadrons produced in association with various trigger objects are balanced as a function of rapidity. It is shown that the observables are sensitive to the model parameters relevant for the minijet production mechanisms:...

40. Quarkonium production as a function of charged-particle multiplicity in pp collisions measured by ALICE at the LHC

Ms Tasnuva Chowdhury (Université Clermont Auvergne (FR))

11/12/2018, 09:40

WG4

Quarkonium (a bound state of $Q\bar{Q}$ pair) production as a function of charged-particle multiplicity has been measured in pp collisions at the LHC. They exhibit a non-trivial correlation that can lead to a better understanding of the multiple-parton interaction mechanism in the initial state of the collision as well as possible collective effects in small systems. The ALICE detector at the...

47. Energy and multiplicity dependence of identified particle production in small systems with ALICE at the LHC

Stefania Bufalino (Politecnico di Torino (IT))

11/12/2018, 10:00

WG4

One of the key results of the LHC Run 1 was the observation of an enhanced production
of strange particles in high multiplicity pp and p-Pb collisions at 7 and 5.02 TeV, respectively.
In addition, the multiplicity dependent results on particle production in pp collisions allowed the discovery of collective-like behavior in small systems at the LHC.
In order to provide further insights into the...

67. Multiplicity dependent J/ψ production in proton-proton collisions with PYTHIA8

Steffen Georg Weber (Technische Universitaet Darmstadt (DE))

11/12/2018, 10:20

WG4

The correlation of charmonium (and also of heavy quarks in general) production with the charged particle multiplicity is of high interest, as it could give new insight into the interplay between hard and soft mechanisms in particle production, both at parton level and at hadronization.
Experimental data shows an intriguing increase of the self-normalized J/ψ yield with multiplicity.
In this...

66. Two-loop splitting in double parton distributions

Jonathan Richard Gaunt (CERN)

11/12/2018, 11:10

WG3

We discuss the computation of the 1->2 splitting functions and matching coefficients at two loops, which are required for the computation of DPS cross sections at NLO.

14. Double Parton Scattering at Short Relative Transverse Distances

Daniele Treleani (University of Trieste)

11/12/2018, 11:30

WG3

The contributions to the Double Parton Scattering cross section, due to pairs of interacting partons generated by perturbative splitting is enhanced at short relative transverse distances, between the centers of mass of the two partonic collisions. One my thus foresee the interesting possibility of discriminating experimentally between contributions to the double parton scattering cross...

5. Jet substructure as a tool to study Double parton scatterings in V + jets processes at the LHC

Dr Ramandeep Kumar (Panjab University (IN))

11/12/2018, 11:50

WG3

Double parton scatterings (DPS) provide vital information on the parton-parton correlations and parton distributions in a hadron. DPS also constitutes as a background to new physics searches. The measurement of DPS in Vector Boson (V) + jets processes is important because of clean experimental signature and large production cross-section. The available DPS measurements, with V + jets, are...

10. Mini-jet model estimate of the effective cross-section for double parton scattering

Giulia Pancheri (INFN Frascati)

11/12/2018, 12:10

WG3

We will present an estimate of the effective cross-section in double parton scattering based on the eikonal minijet model with soft gluon resummation, which was recently applied to the calculation of the total and inelastic non-diffractive proton proton cross-section at LHC and to the estimate of survival probabilities at LHC. Comparison with results from an empirical model modified to take...

42. Double parton scattering in final states with jets

Deepak Kar (University of the Witwatersrand (ZA))

11/12/2018, 12:30

WG3

Though already thirty years have passed since the double parton scattering (DPS) effects have been observed for the first time, a strong interest to this topic still persists. In spite of large theoretical and experimental progress, a lot of space is left for improvement of our understanding of the DPS mechanisms. Certain advantages are provided by studies performed in various final states, in...

76. Prospects and results from the AFP detector in ATLAS

Dr Vlasios Petousis (Czech Technical University (CZ))

11/12/2018, 15:00

WG5

Prospects and results from the AFP detector in ATLAS

74. Hadronic interactions in cosmic ray and astro-particle physics

Anatoli Fedynitch (DESY)

11/12/2018, 15:20

WG5

In my talk I will highlight a number of recent developments in particle astrophysics that interface with high-energy physics. A particular focus lies on the importance of hadronic interaction models for the interpretation of Ultra-High Energy Cosmic Ray observations.

70. Soft QCD and small-x physics at the LHC and beyond

Hans Van Haevermaet (University of Antwerp (BE))

11/12/2018, 15:40

WG5

The description of collisions involving hadrons has always been a challenging task, especially at nonperturbative scales and the forward phase space. Being at the end of LHC Run 2 an overview of recent measurements and developments in soft QCD and small-x physics at the LHC is presented, together with remaining open questions and an outlook for future studies that are still missing to improve...

78. Inclusion of open heavy-flavour data in PDF fits

Maria Vittoria Garzelli

11/12/2018, 16:00

WG5

I will discuss about the impact of open heavy-flavour data on the gluon and sea quark PDFs in the low x/low Q2 region and the still open problems in the fitting procedure, with examples/considerations from the experience with the PROSA and the ABMP PDF fits.

77. Jet veto cross section measurements in ATLAS

Andy Buckley (University of Glasgow (GB))

11/12/2018, 16:20

WG5

Jet veto cross section measurements in ATLAS

34. Electron-Ion Collider: where do we stand?

Marco Radici

11/12/2018, 17:10

WG6

The Electron-Ion Collider (EIC) is the project for a new US-based high-energy high-luminosity facility, capable of a versatile range of beam energies, polarizations, and ion species. Its primary goal is to precisely image quarks and gluons and their interactions inside hadrons, in order to investigate their confined dynamics and elucidate how visible matter is made at its most fundamental...

9. Implications of MPI in ALICE multiplicity measurements

Valentina Zaccolo (Universita e INFN Trieste (IT))

11/12/2018, 17:40

WG6

Multiple Partonic Interactions (MPI) refer to those cases where more than one semi-hard partonic scattering occurs within the same pp collision. Their relevance increases at high collision energies. Therefore, it is crucial to deepen the understanding of MPI contributions to particle production in hadronic collisions at the LHC.
ALICE has performed several measurements in small collision...

3. Multiple parton interactions and collectivity in the context of a two-component model of hadron production

Prof. Thomas Trainor (University of Washington)

11/12/2018, 18:00

WG6

A two-component (soft + hard) model (TCM) of hadron production in high-energy nuclear collisions has been applied to $p_t$ spectra, particle densities on $\eta$, 2D angular correlations and total yields from p-p, p-A and A-A collisions and provides a self-consistent description of charge-multiplicity and collision-energy dependence for a broad array of data. The TCM provides alternative...

38. System Size Dependence of Heavy Flavor and Quarkonia Production at RHIC

Dr Rachid Nouicer (Brookhaven National Laboratory (BNL, USA))

11/12/2018, 18:20

WG6

Particles carrying heavy flavor are important probes to study the properties of the Quark-Gluon Plasma (QGP) created in relativistic heavy-ion collisions at RHIC. They are produced in hard scattering during the earliest stages of nuclear collisions and, because of their high mass, theoretical calculations are more tractable than those involving light quarks. The RHIC experiments have collected...

63. Low pT direct photon production at PHENIX in small-on-large collisions

Dr Balazs Ujvari (University of Debrecen)

11/12/2018, 18:40

WG6

PHENIX has measured low pT direct photon yields and elliptic flow in 200 GeV Au+Au collisions with three different methods and the results are consistent. The yield measurements have been extended to lower collision energies and different colliding systems. It has been found that the integrated yields scale with the respective charged particle density, independent of system size, collision...

16. Recent results on Minimum Bias and Underlying Event by CMS

Valentina Mariani (Universita e INFN, Perugia (IT))

12/12/2018, 09:00

WG1

The talk will present the most recent results obtained by the CMS collaboration on minimum bias processes and the so-called underlying event.

1. From Underlying Event Sensitive To Insensitive: Factorization and Resummation

Yiannis Makris

12/12/2018, 09:20

WG1

In this talk we will discuss the transverse energy spectrum for the Drell-Yan process. The transverse energy is measured within the central region defined by a (pseudo-) rapidity cutoff. Soft-collinear effective theory (SCET) is used to factorize the cross section and resum large logarithms of the rapidity cutoff and ratios of widely separated scales that appear in the fixed order result. We...

26. Fragmentation studies with the ATLAS detector

Sergio Calvente Lopez (Universidad Autonoma de Madrid (ES))

12/12/2018, 09:40

WG1

Abstract: Gluon splitting to b-quark pairs is a unique probe into the properties of gluon fragmentation, as identified b-tagged jets provide a proxy for the quark daughters of the initial gluon. If available, we present a measurement of key differential distributions related to g→b bbar using data collected with the ATLAS detector at √s=13 TeV. Track jets are used to probe angular scales below...

58. Physics of small collision systems using UE observables

Antonio Ortiz Velasquez (Universidad Nacional Autonoma (MX))

12/12/2018, 10:00

WG1

In this work we study the underlying event (UE) activity as a function of the highest jet transverse momentum ($p_{\rm T}^{\rm jet}$) in terms of the number and summed $p_{\rm T}$ densities of charged particles in the azimuthal region transverse to the $p_{\rm T}^{\rm jet}$ direction. The UE activity considering charged particles within different $p_{\rm T}$ intervals in $pp$ collisions at...

27. Jet Substructure Measurements with the ATLAS Detector

Miguel Villaplana (Università degli Studi e INFN Milano (IT))

12/12/2018, 10:20

WG1

Abstract: Calculations of jet substructure observables which are accurate beyond leading-logarithmic accuracy have recently become available. Such observables are significant not only for probing a new regime of QCD at a hadron collider, but also for improving the understanding of jet substructure properties that are used in many studies at the Large Hadron Collider. In this talk, we discuss...

57. Efficient numerical evolution of double-parton distributions

Mr Riccardo Nagar (Deutsches Elektronen-Synchrotron DESY)

12/12/2018, 11:10

WG3

Practical solutions to the evolution equations for double-parton distributions (DPDs) that are accurate but feasible in terms of computing resources are a challenging task in the study of double-parton scattering phenomenology in perturbative QCD. Due to the higher dimensionality of DPDs with respect to single PDFs, a simple extension of the available methods for PDF evolution is...

56. Colour Reconnection from Soft Gluon Evolution

Mr Patrick Kirchgaesser (KIT)

12/12/2018, 11:30

WG3

We consider soft gluon evolution of a system of clusters forming the initial state of the cluster hadronziation model, in order to constrain colour reconnection models from a perturbative point of view.
We show that this ansatz produces clusters with properties attributed to
a colour pre-confined state and find strong evidence for formerly investigated colour reconnection models based on...

53. Constraining DPD models using sum rules

Peter Plößl (University of Regensburg)

12/12/2018, 11:50

WG3

Double parton distributions (DPDs) are not only an essential building block
needed in factorization theorems to calculate double parton scattering (DPS)
cross sections in perturbation theory, but they also contain very detailed
information about hadronic structure. However, as presently an extraction of
DPDs from experimental data or lattice calculations is not yet feasible, it is
common...

59. Double Parton Distributions for the Pion on the Lattice

Mr Christian Zimmermann (Universität Regensburg)

12/12/2018, 12:10

WG3

Double parton distributions (DPDs) are an important piece in the description of double hard interactions. On the lattice we calculate correlation functions of two local quark currents, which can be related to Mellin moments of DPDs. For the first moment we calculate all contributing Wick contractions for the pion, considering several channels corresponding to the quark polarization....

48. Studies of the double parton scattering using massive vector bosons

Ankita Mehta (Eötvös University, Budapest)

12/12/2018, 12:30

WG3

The thirty-year long history of the studies of the double parton scattering (DPS) lead to a large number of measurements in various channels and wide range of the collisions energies. At the LHC era the role of the DPS in the production processes becomes more and more significant as its contribution is expected to increase at higher energies. Estimates of this contribution provide an important...

80. free time in Perugia downtown

12/12/2018, 15:00

Excursion

79. Guided Tour of Perugia Downtown (for registered participants)

12/12/2018, 16:30

Excursion

Meeting point for Tour Leaders and Participants:
- hotel "La Rosetta" at 4:30 PM

81. free time in Perugia downtown

12/12/2018, 18:30

Excursion

35. Prospects and results from the PPS detector

Enrico Robutti (INFN e Universita Genova (IT))

13/12/2018, 09:00

WG5

The talk will present prospects and results from the precise proton-spectrometer (PPS), a new detector born from the collaboration between the CMS and TOTEM experiments at the LHC

68. Total, elastic and inelastic cross section measurements in TOTEM

Giuseppe Latino (Universita e INFN, Firenze (IT))

13/12/2018, 09:20

WG5

The TOTEM experiment, located at the interaction point 5 of the LHC, has measured the total, elastic and inelastic proton-proton cross sections in a centre-of-mass energy range from 2.76 to 13 TeV, mostly in dedicated fills with special beam optics. Most recently, TOTEM has performed a series of detailed measurements at √s = 13 TeV. The total, elastic and inelastic proton-proton cross-sections...

36. CMS results on diffraction and exclusive production

Hans Van Haevermaet (University of Antwerp (BE))

13/12/2018, 09:40

WG5

The talk will present an overview of the results on diffraction and exclusive production obtained by the CMS experiment at the LHC

45. Diffractive electroproduction of $\rho$-meson as discriminating testfield for the unintegrated gluon distribution in the proton

Andrèe Dafne Bolognino (Università della Calabria & INFN gruppo collegato Cosenza)

13/12/2018, 10:00

WG5

The unintegrated gluon distribution (UGD) encodes the gluon content in the proton in the high-energy domain and gives the probability that a gluon can be emitted by a colliding proton, with given longitudinal momentum fraction and transverse momentum. The UGD, being a nonperturbative quantity, it is not well known and several models for it have been introduced so far.
The diffractive...

62. Central Exclusive Production at LHCb

Daria Savrina (M.V. Lomonosov Moscow State University (RU))

13/12/2018, 10:20

WG5

With installation of new shower counters (HERSCHEL) along the beampipe the sensitivity of the LHCb experiment to the central exclusive production (CEP) has significantly increased. And the dedicated triggers introduced in the early period of Run 2 allowed to extended dataset for the CEP measurements.
The talk will cover the CEP results of LHCb experiment during Run1 and Run2

44. Studies of the Double parton scattering through heavy flavours production

Aleksei Dziuba (Petersburg Nuclear Physics Institut (RU))

13/12/2018, 11:10

WG3

During last thirty years presence of the double parton scattering (DPS) in the hadronic collisions has been demonstrated by a large number of experiments. Though the underlying mechanisms are still poorly understood. Studies of the events involving heavy flavour production allow to reach very small transverse momentum regions and to test the factorization approach to the DPS description with...

61. Proton Structure at the LHC via double parton scattering

Federico Alberto Ceccopieri (Universita & INFN, Milano-Bicocca (IT))

13/12/2018, 11:40

WG3

We discuss double parton distribution functions (dPDFs), the main non perturbative ingredients appearing in the double parton scattering cross section (DPS) formula in hadronic collisions. By using recent calculations of dPDFs within Light-Front constituent quark models [1], we investigate the role of correlations induced by relativistic effects on dPDF evaluations [2]. Such distributions...

8. A spin on same-sign W boson pair production at the LHC

Sabrina Cotogno (Nikhef)

13/12/2018, 12:00

WG3

In double parton scattering processes, the interparton correlations can have an impact on the size of the cross section and significantly alter the distributions of particles in the final state.
We focus on the production of a pair of W bosons with the same electric charge. We demonstrate that the LHC has the potential to extract non-trivial information on spin-correlations between two quarks...

12. Four-jet and three-jet plus gamma DPS production in pp and pA collisions at the LHC

Oleh Fedkevych (Lund University)

13/12/2018, 12:20

WG3

In spite of the recent progress in both theoretical and experimental studies many aspects of multiple parton interactions (MPI) still require a detail investigation. In particular, double parton scattering (DPS) processes can play a dominant role for some specific kinematic regions of multi-jet production, especially in proton-nucleus (pA) collisions where the total DPS cross section...

6. Double parton scatterings in associated-quarkonium production

Nodoka Yamanaka (Riken)

13/12/2018, 12:40

WG3

Recent studies of associated-quarkonium production at the LHC and the Tevatron have pointed at values of $\sigma_{\rm eff}$ significantly smaller than those extracted from jet-related observables, on the order of 5-10 mb. Other studies carried out by LHCb in the forward rapidity region pointed at more usual values close to 15-20 mb. I will report on these and propose possible explanations for...

72. LHC as a photon collider

Christophe Royon (The University of Kansas (US))

13/12/2018, 15:00

WG5

We will discuss the measurements of exclusive di-photon events at the LHC in pp and Pb Pb runs. these events lead to the best possible sensitivities to quartic anomalous couplings between photons, Z and W bosons. We will also give the sensitivities to the search for axion like particles at high mass.

73. The Electron Ion Collider and its implications for high-energy phenomenology

TIMOTHY J HOBBS (Southern Methodist University)

13/12/2018, 15:20

WG5

A future electron-ion collider (EIC) will be a dedicated high-luminosity machine with the capability of unraveling many issues in QCD, including a systematic tomographic mapping of the nucleon's internal structure, investigations of the quark-hadron transition, the onset and dynamics of gluon saturation at low x, and the nature of the nuclear medium. In addition to the wealth of information...

51. Probing colour reconnection using boosted hadronically decaying top quarks

Deepak Kar (University of the Witwatersrand (ZA))

13/12/2018, 15:40

WG2

One of the largest uncertainty in many top quark measurements is the one on the modelling of colour reconnection (CR) between top quark decay products. There have been several experimental measurements, notably of the pull angle in $t\overline{t}$ events, which were intended to provide useful input to CR modelling, but we have not seen strong sensitivity. In this presentation, we propose a...

21. Teaching PROFESSOR New Math

Holger Schulz (Fermilab)

13/12/2018, 16:00

WG2

We present a range of improvements to the model parameter tuning program Professor. A severe limitation of the so far applied polynomial surrogates, namely the capture of $\frac{1}{x}$ behaviour of functional forms, is overcome
by a new algorithm that calculates multivariate rational approximations thus allowing for more truthful approximations and wider applicability of the method.
We also...

15. MC Modelling and Tuning in CMS

Gurpreet Singh Chahal (Imperial College and IPPP Durham University (GB))

13/12/2018, 16:20

WG2

A new set of CMS underlying-event tunes is presented for the PYTHIA 8 event generator. The tunes use the NNPDF3.1 parton distribution functions at leading (LO), next-to-leading (NLO), or next-to-next-to-leading (NNLO) order in perturbative quantum chromodynamics, and the strong coupling evolution at LO or NLO. Comparisons of the predictions of the new tunes are provided for observables...

60. Investigating the flow-like correlations with new possibility

You Zhou (University of Copenhagen (DK))

13/12/2018, 17:10

WG4

Multiple experimental measurements have shown strong indications of flow in small collision systems. In this talk, I will examine the selected theoretical models with latest as well as well hidden experimental results in small collisions systems. I will discuss which experimental ''evidence" is solid and which might be misinterpreted. In addition, I will show the potential of deep learning in...

43. Effects of geometry initial-state fluctuations on the ridge structure in pp collisions.

Irais Bautista Guzman (Autonomous University of Puebla (MX))

13/12/2018, 17:40

WG4

One of the key signatures of collectivity in heavy-ion collisions is the appearance of a ridge structure over wide pseudorapidity interval. Recently it was also found in small collision systems such as proton-proton or proton-ion collisions which origin is still on debate. In this work, contributions from the geometry fluctuations in the initial-state in pp collisions to the ridge structure...

52. Collectivity and MPI

Boris Blok (Physics Department)

13/12/2018, 18:00

WG4

We develop a MPI based theory of ridge phenomena in `MPI, the origin of collectivity comes out to be quantum interference of different MPIs. We show that
in this approach we obtain a picture of ridge phenomena in pp collisions compatible both qualitatively and qualitatively with experimental data.
the talk is based on:
Collectivity from interference
Boris Blok (Technion), Christian D. Jäkel...

90. Introduction

Paolo Bartalini (Central China Normal University CCNU (CN))

13/12/2018, 18:30

Steering

91. next host candidature: Prague

Miroslav Myska (Czech Technical University (CZ))

13/12/2018, 18:40

Steering

92. next host candidatures: Others

13/12/2018, 18:50

Steering

93. WG4 (High Multiplicity) - Summary

Robert Vertesi (Hungarian Academy of Sciences (HU))

14/12/2018, 09:10

WG4

94. Discussion

14/12/2018, 09:20

WG4

82. WG1 (Minimum Bias and Underlying Event) - Summary

Richard Dryden Field (University of Florida (US))

14/12/2018, 09:40

WG1

83. Discussion

14/12/2018, 09:50

WG1

84. WG2 (MC Generators and Tuning) - Summary

Andy Buckley (University of Glasgow (GB))

14/12/2018, 10:10

WG2

85. Discussion

14/12/2018, 10:20

WG2

86. WG3 (Double Parton Scattering) - Summary

Matteo Rinaldi (Perugia University and INFN, Perugia)

14/12/2018, 11:10

WG3

87. Discussion

14/12/2018, 11:20

WG3

88. WG5 (Low x and Diffraction) - Summary

Michele Gallinaro (LIP Lisbon)

14/12/2018, 11:40

WG5

89. Discussion

14/12/2018, 11:50

WG5

95. WG6 (Heavy Ions) - Summary

Valentina Zaccolo (Universita e INFN Trieste (IT))

14/12/2018, 12:10

WG6

96. Discussion

14/12/2018, 12:20

WG6

4. $\chi_{c}$ pair production with large rapidity distance and extra gluon emission

Ms Izabela Babiarz (Institute of Nuclear Physics, Polish Academy of Science)

Cancelled

Recently there has been much interest in the pair production of
quarkonia. The production of quarkonium pairs is expected to receive
an important contribution from double parton scattering (DPS) processes.
There remain a number of open problems, especially with the CMS and ATLAS data.
The effective cross sections $\sigma_{\rm eff}$ found
from empirical analyses are about a factor $2.5$ smaller...

71. A full set of TMD splitting functions in High Energy Factorization

Mirko Serino

Cancelled

Interpolating exactly between collinear and BFKL evolution has been a desire of the QCD community for a long time. Generelizing the method of Curci, Furmanski and Petronzio for the computation of collinear splitting functions, in the wake of previous work by Catani and Hautmann, we provide the real parts of a full set of TMD splitting functions which match the DGLAP, BFKL and CCFM kernels in...

25. ATLAS results on quarkonia and its associated production

Collaboration ATLAS

Cancelled

Abstract: The associated production of vector boson with quarkonia is a key observable for understanding the quarkonium production mechanisms, including the separation of single and double parton scattering components.
This talk will present the latest differential measurements from ATLAS on quarkonium and associated quarkonium production.

46. Azimuthal asymmetries in the Color glass condensate

Dr Vladimir Skokov (Brookhaven national laboratory)

Cancelled

The origin of long-range rapidity correlations observed in p-p and p-Pb collisions at LHC is one of the outstanding questions of strong interactions. The leading theoretical explanations of the so-called "ridge" effect are hydrodynamics and the initial state dynamics, with the latter often described in the Color Glass Condensate (CGC) framework. CGC-based calculations have successfully...

20. Latest results on double parton scattering measurements from the CMS experiment

Collaboration CMS

Cancelled

Results on the measurement of double parton scattering processes will be reported based on the Run-I and Run-II high-luminosity data collected in proton-proton running using the CMS experiment. A future outlook of the studies will be presented for the upcoming high-luminosity LHC data-taking periods.

28. Measurement of distributions sensitive to the underlying event in inclusive Z-boson production in pp collisions at ¿s = 13 TeV with the ATLAS detector

Andreas Warburton (McGill University, (CA))

Cancelled

Abstract: A measurement of charged-particle distributions sensitive to the properties of the underlying event is presented for an inclusive sample of events containing a Z-boson, decaying to a muon pair. Distributions of the charged particle multiplicity and of the charged particle transverse momentum are measured in regions of azimuthal angle defined with respect to the Z-boson direction. The...

30. Monte Carlo generator for the modelling of multijet processes in ATLAS at 13 TeV

Collaboration ATLAS

Cancelled

Abstract: Most of the interesting physics at the LHC involves final states with hadronic jets.

We present Monte Carlo event generator configurations used by the ATLAS experiment

to model multi-jet processes in pp collisions at 13 TeV.
The generators are compared to each other for kinematic distributions sensitive both to the kinematic of hard process and to shower and non-perturbative...

19. MPI and heavy ions: CMS results

Collaboration CMS

Cancelled

The talk will report on the most recent results obtained by the CMS experiment on multiple partonic interactions in heavy-ion collisions

33. Multi-parton scattering effects in heavy flavour production at the LHC

Rafal Maciula (Institute of Nuclear Physics PAN)

Cancelled

In this talk I will summarize results of our studies of hard MPI effects in heavy flavour sector in pp-collisions at the LHC. During last two years we extend our previous studies of double-parton scattering (DPS) in double charm production to simultaneous production of charm and bottom as well as to double bottom production. We have also analyzed in this context associated production of charm...

2. Particle multiplicities in the central region of high-energy collisions from $k_T$-factorization with running coupling corrections

Andre Veiga Giannini

Cancelled

Horowitz and Kovchegov have derived a $k_T$-factorization formula for particle production at small $x$ which includes running coupling corrections. We perform a first numerical analysis to confront the theory with data on the energy and centrality dependence of particle multiplicities at midrapidity in high-energy p+A (and A+A) collisions. Moreover, we point out a strikingly different...

37. Recent results from TOTEM/CMS

Collaboration CMS

Cancelled

The talk will present an overview of the most recent results obtained by the TOTEM and CMS experiments on the so-called forward physics

17. Small system physics from CMS: energy and multiplicity dependence of identified particle production

Collaboration CMS

Cancelled

The CMS collaboration presents two contributions on small-system physics. This contribution will specifically focus on the dependence of identified particle production on energy and multiplicity.

31. Status of measurements of diffractive processes with the ATLAS detector

Collaboration ATLAS

Cancelled

Abstract: The status of diffractive measurements at the ATLAS experiment will be presented. Diffractive dijet production was identified using empty regions of the ATLAS detector (so-called rapidity gaps). The data are compared with Monte Carlo models and the rapidity gap survival probability has been estimated in the kinematic region with high diffractive contribution. If available, we will...

75. Theoretical uncertainties at small x and kT-improved collinear calculations

Benjamin Guiot, (Valparaiso)

Cancelled

Theoretical uncertainties at small x and kT-improved collinear calculations