Opportunities of OO and pO collisions at the LHC

4 Feb 2021, 14:25 → 10 Feb 2021, 19:05 Europe/Zurich

Zoom (CERN)

Jasmine Therese Brewer (CERN), Aleksas Mazeliauskas (CERN), Wilke van der Schee (CERN)

A summary of the workshop is available at arXiv:2103.01939

---

The goal of this 5-day workshop is to explore the community perspective on the physics opportunities of oxygen-oxygen and proton-oxygen collisions in the LHC Run 3.

The cosmic-ray community argues for a short pO run during Run 3, because this is the unique time-window for LHCf to take data. In the heavy-ion community, the origin of collectivity in small collision systems remains a central question that begs a timely answer. A more formalised exchange between LHC experiments and theory is clearly an advantage for a successful pO and OO run. Through this workshop, we aim to bring together theorists and experimentalists to discuss both the physics opportunities and challenges specific to OO and pO.

The workshop will provide time for creative discussions on unique opportunities from collisions of light ions. A short summary document of the main conclusions of the workshop will be prepared in advance of the LHCC meeting in March 2021.

Programme:

• Light-ion beams at the LHC
• Initial state
• Soft dynamics of small systems
• Hard probes in OO and pO
• Experimental opportunities with OO and pO
• pO for cosmic-ray physics

Confirmed speakers:

• Reyes Alemany Fernandez (CERN)
• Roderik Bruce (CERN)
• Martino Gagliardi (Universita di Torino)
• Wojciech Broniowski (IFJ PAN & UJK)
• Soeren Schlichting (Universität Bielefeld)
• Wenbin Zhao (Peking University)
• Chun Shen (Wayne State University)
• Harri Niemi (University of Jyväskylä)
• Govert Nijs (MIT)
• Yuuka Kanakubo (Sophia University)
• Petja Paakkinen (Universidade de Santiago de Compostela)
• Alexander Huss (CERN)
• Liliana Apolinário (LIP)
• Jacquelyn Noronha-Hostler (University of Illinois at Urbana-Champaign)
• Man Xie (Central China Normal University)
• Vytautas Vislavicius (ALICE, Copenhagen University)
• Igor Altsybeev (ALICE, St Petersburg State University)
• Anne Marie Sickles (ATLAS, Univ. Illinois at Urbana Champaign)
• Michael Murray (CMS, University of Kansas)
• Hans Dembinski (LHCb, MPI Heidelberg)
• Giacomo Graziani (LHCb/SMOG, INFN Firenze)
• Hiroaki Menjo (LHCf, Nagoya University)
• Alessio Tiberio (LHCf, Universita e INFN, Firenze)
• Tanguy Pierog (KIT, IAP)
• Dennis Perepelitsa (sPHENIX, CU Boulder)
• Wei Li (STAR, Rice University)
• Christian Bierlich (Lund University)

The workshop will take place over five days with a weekend break in the middle: Feb 4-5 and Feb 8-10. Four to five talks each day are scheduled in the late afternoon Geneva time to accommodate different time zones. Each day will be concluded with an extended discussion session to allow an in-depth analysis on the unique opportunities of OO and pO collisions at the LHC.

All talks will be held virtually on Zoom (registration is mandatory to access the links).

oo_poster_final.pdf

oo_screen_HD.jpg

Thursday 4 February

14:25 → 14:30 Opening

Speaker: Michelangelo Mangano (CERN)

Introduction_MLM.pdf

14:30 → 15:50 Light-ion beams at the LHC

Convener: Dr Marc Andre Jebramcik (DESY (DE))

14:30 Preparing the CERN Ion Injector Chain for an LHC Oxygen Run

The preparation of the CERN Ion Injector Chain for an LHC Oxygen Run is not straight forward because the Complex has been designed to deliver Lead beams with a very low radiological impact. With Oxygen beams, initial simulations indicate that we cross the safety borders in terms of personnel and equipment protection. Therefore, special measurements need to be put in place. However, there is nonetheless something positive about Oxygen production, it gives much more beam intensity than Lead, which is really an advantage because LHC can quickly accumulate luminosity. In this talk we summarise the beam intensity expectation across the Ion Injector Complex up to the LHC injection, together with an explanation of the different studies and special measurements that have to be put in place to realise such a run in the CERN Ion Injector Chain.

Speaker: Reyes Alemany Fernandez (CERN)

oo_opportunities_at_LHC_alemany.pdf

oo_opportunities_at_LHC_alemany.pptx

Recording

15:00 LHC machine scenario for a short oxygen run

This talk discusses scenarios for a short oxygen run in the LHC in terms of needed commissioning, machine constraints, beam parameters, and estimated luminosity performance. Both O-O and p-O collisions are discussed.

Speaker: Dr Roderik Bruce (CERN)

2021.02.04--OO_pO_workshop--LHC_machine_scenarios.pdf

2021.02.04--OO_pO_workshop--LHC_machine_scenarios.pptx

Recording

15:30 Luminosity determination with heavy-ion beams at the LHC

Speaker: Martino Gagliardi (Universita e INFN Torino (IT))

Gagliardi_OppO_040221_v6.pdf

Recording

15:50 → 16:15 Discussion

Conveners: Dr Georgios Krintiras (The University of Kansas (US)), Gian Michele Innocenti (CERN), John Jowett (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

15:50 Discussion on machine development and luminosity

Speakers: Georgios Krintiras (The University of Kansas (US)), Gian Michele Innocenti (CERN), John Jowett (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))

20210204_DiscussionSession.pdf

16:15 → 16:30 Coffee break

16:30 → 18:05 Initial state

Convener: Dekrayat Almaalol (Kent State University)

16:30 Eccentricities in collisions with 16O and 12C

I will cover eccentriciteis in collisions with 16O and also 12C, with emphasis on sensitivity to nuclear correlations, in particular, alpha clusterization. Realistic nuclear distribution will be considered and prospects of experimental signatures discussed.

Speaker: Wojciech Broniowski (IFJ PAN)

O16.pdf

Recording

17:10 Initial state and non-equilibrium dynamics in small and large systems

Speaker: Prof. Soeren Schlichting (Universität Bielefeld)

Recording

SchlichtingOO21.pdf

17:50 Coffee break

18:05 → 18:30 Discussion

Conveners: Giuliano Giacalone (Université Paris-Saclay), Jiangyong Jia (Stony Brook University (US)), Yi Yin (IMP)

18:05 Discussion on initial state

Speakers: Giuliano Giacalone (Université Paris-Saclay), Jiangyong Jia (Stony Brook University (US)), Yi Yin (IMP)

OO_discussion.pdf

Friday 5 February

14:30 → 15:50 Soft dynamics of small systems

Convener: Huichao Song

14:30 Collectivity and QGP signals in Large and Small systems

Speaker: Wenbin Zhao (Peking University)

OppO_Workshop_Wenbin_Zhao.pdf

Recording

15:10 Dynamical Modeling of the Collectivity in pO and OO Collisions

Small collision systems, such as pO and OO, can provide valuable information about the collisions' early-stage dynamics. They also present high sensitivity to initial state fluctuations at multiple length scales. In this talk, we employ the hybrid IP-Glasma + hydrodynamics + hadronic transport approach to simulate the pO and OO collisions' bulk dynamics at the LHC energies. All the model parameters were fixed in the large heavy-ion collisions. We will discuss the challenges of extrapolating the hydrodynamic description to these small systems and identify new aspects of the many-body properties of the hot QCD matter these small systems can probe.

Speaker: Dr Chun Shen (Wayne State University)

OO_and_pO.pdf

Recording

15:50 → 16:05 Coffee break

16:05 → 17:25 Soft dynamics of small systems

Convener: Derek Everett (Ohio State University)

16:05 Multiplicity and flow in O+O collisions from the EKRT model

We extend the computed EKRT initial conditions from 5 TeV Pb+Pb collisions to O+O collisions at the same collision energy, and compute the subsequent fluid dynamical evolution. We show preliminary predictions for multiplicity and flow observables, and compare the results to the peripheral Pb+Pb collisions at the same collision energy and multiplicity.

Speaker: Harri Niemi (Johann Wolfgang Goethe-Universität)

oppo_Niemi.pdf

Recording

16:35 Bayesian Analysis of Oxygen-Oxygen Collisions

We use the Trajectum heavy ion code to generate predictions for OO observables, where we use model parameters which are fitted to PbPb data. We subsequently use the OO predictions as mock data for a Bayesian analysis which includes both the PbPb and OO systems, which allows us to estimate the impact of the future addition of OO data on the quality of Bayesian analyses.

Speaker: Govert Nijs (Massachusetts Institute of Technology)

Recording

trajectumtalk.pdf

17:05 Hadron yield ratios in dynamical core-corona initialization from small to large systems

The quark-gluon plasma (QGP) formation in small colliding systems is implied from various experimental data at LHC and RHIC. Focusing on one of them, the particle yield ratio, we investigate a possibility of the QGP formation through the dynamical core{corona initialization (DCCI) model. We extend the conventional core{corona picture introducing it into the dynamical initialization framework and demonstrate a dynamical separation of core and corona. In this talk, I give motivation and detailed modeling of the DCCI, and show results of particle yield ratios as a function of multiplicity in p-p, p-Pb and Pb-Pb collisions. I also mention some thoughts on particle yield ratios in p-O and O-O collisions.

Speakers: Tetsufumi Hirano (Sophia Univ), Yuuka Kanakubo (Sophia Univ.)

Recording

YK-TH_OPPO2_figures.pdf

17:25 → 17:40 Coffee break

17:40 → 18:30 Discussion

Conveners: Bjoern Schenke (Brookhaven National Lab), Jean-Francois Paquet (Duke University), You Zhou (Niels Bohr Institute (DK))

17:40 Discussion on hydrodynamic modelling

Speakers: Bjoern Schenke (Brookhaven National Lab), Jean-Francois Paquet (Duke University), You Zhou (Niels Bohr Institute (DK))

discussion.pdf

Monday 8 February

14:30 → 15:40 Hard probes in pO and OO

Convener: Michael Klasen

14:30 Current status of nPDFs and prospects for pO and OO collisions

The global analyses of nuclear parton distribution functions (nPDFs) are going through a phase of rapid development, driven mainly by new constraints from the CERN LHC proton–lead program, and attracting also new groups to join the field. In this talk, I will review the current status of nPDF global analyses. I will concentrate on the opportunities with lighter-ion runs at the LHC and in particular on the prospects of the proposed proton–oxygen (pO) and oxygen–oxygen (OO) collisions in constraining the mass-number dependence of the nPDFs. As a case study, I will present predictions for dijet production at pO, which has a sizable cross section at the 9.9 TeV collision energy and can thus be expected to give constraints for gluon nuclear modifications even at relatively low luminosities.

Speaker: Petja Paakkinen (IGFAE - Universidade de Santiago de Compostela)

nPDF_OppOrtunities_Paakkinen.pdf

Recording

15:10 Discovering partonic rescattering in light nucleus collisions

Speaker: Alexander Yohei Huss (CERN)

OppO_Huss.pdf

Recording

15:40 → 15:55 Coffee break

15:55 → 17:25 Hard probes in pO and OO

Convener: Dr Isobel Kolbe (Institute for Nuclear Theory)

15:55 Jet Quenching from light to dense systems

Results on pA collisions have demonstrated the potential of light systems in achieving the most surprising discoveries. The presence of fluid-like behaviour and their implications motivate further the determination of the necessary conditions that mark the onset of the QGP phase. Intermediate systems, like pO and OO, will be invaluable to a successful unified particle production description from small (pp) to larger (AA) systems. Signatures of medium-induced modifications in the hard sector were, so far, unexistent, or quite limited, putting additional stress on the accurate determination of theoretical and experimental uncertainties. In this talk, we aim to discuss novel theoretical and experimental methodologies, focusing on pO and OO, to characterise the short-wavelength QGP properties with unprecedented precision.

Speaker: Liliana Apolinario (LIP (PT))

OppO_LApolinario.pdf

Recording

16:25 The elusive energy loss signal of the Quark Gluon Plasma in OO collisions

Speaker: Prof. Jacquelyn Noronha-Hostler (University of Illinois Urbana Champaign)

JNH_OO2021.pdf

Recording

17:05 $\gamma$-hadron spectra in $p$ + Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV

Under the assumption that a quark-gluon plasma droplet is produced and its evolution can be described by hydrodynamics in p + A collisions, $\gamma$-triggered hadron spectra \cite{Wang:1996yh, Zhang:2009rn} are studied within a next-to-leading-order perturbative QCD parton model with the medium-modified parton fragmentation functions. The initial conditions and space-time evolution of the small QGP droplet are provided by the superSONIC hydrodynamic model \cite{Weller:2017tsr} simulations and parton energy loss in such a medium is described by the high-twist (HT) approach \cite{Wang:2009qb}. The range of scaled jet transport coefficient $\hat{q}_0/T_0^3$ in this HT approach is extracted from single hadron suppression in A + A collisions with similar initial medium temperature as in p + A collisions. Numerical results for this scenario show that $\gamma$-hadron spectra at $p_{\rm T}^\gamma=12-40$ GeV/$c$ are suppressed by 5 $-$ 15\% in the most central 0 - 10\% p + Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV. The suppression becomes weaker at higher transverse momentum of the $\gamma$ trigger. As a comparison, $\gamma$-hadron suppression in Pb + Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ and 5.02 TeV is also predicted.

Speaker: Man Xie (Central China Normal University)

gam-had-OO-xieman.pdf

Recording

17:25 → 17:40 Coffee break

17:40 → 18:30 Discussion

Conveners: Carlota Andres (LIP, Lisbon), Marco Van Leeuwen (Nikhef National institute for subatomic physics (NL)), Dr Xin-Nian Wang (Lawrence Berkeley National Lab. (US))

17:40 Discussion session on hard probes

Speakers: Carlota Andres (LIP, Lisbon), Marco Van Leeuwen (Nikhef National institute for subatomic physics (NL)), Xin-Nian Wang (Lawrence Berkeley National Lab. (US))

Tuesday 9 February

14:30 → 15:50 Experimental opportunities with OO and pO

Convener: Deepa Thomas (University of Texas at Austin (US))

14:30 ALICE goals and projections for hard probes measurements

Speaker: Vytautas Vislavicius (University of Copenhagen (DK))

Recording

VVislavicius_OOpOrtunities.pdf

14:50 ALICE goals and projections for flow and hadron production/interaction measurements

Speaker: Igor Altsybeev (St Petersburg State University (RU))

ALICE_Flow_Femto_nuclei_UPC.pdf

Recording

15:10 ATLAS contribution

Speaker: Anne Marie Sickles (Univ. Illinois at Urbana Champaign (US))

Recording

sickles_020921.pdf

15:50 → 16:05 Coffee break

16:05 → 17:25 Experimental opportunities with OO and pO

Convener: Austin Alan Baty (Rice University (US))

16:05 Physics opportunities with oxygen collisions in CMS

Oxygen on oxygen, proton oxygen and photon oxygen collisions at the LHC offer rich physics opportunities both in themselves and as compliments to the current lead based heavy ion program. The extensive rapidity coverage, excellent event reconstruction, and flexible trigger system of CMS make it an ideal detector for exploiting such opportunities. This talk will review potential oxygen measurements with CMS and describe some of the challenges in making such measurements a reality.

Speaker: Michael Murray (The University of Kansas (US))

MurrayOxygenOpportunities.pdf

Recording

16:45 Oxygen beams and LHCb: prospects of pO and OO collisions for nuclear and astroparticle physics

Speaker: Dr Hans Peter Dembinski (TU Dortmund)

Recording

talk.pdf

17:05 Oxygen beams and LHCb: prospects of collisions with fixed-targets

The LHCb experiment has the unique possibility, among the LHC
experiments, to be operated in fixed target mode using its internal gas
target. After reviewing the results achieved so far in the fixed target
configuration, we will discuss prospects for the incoming run, where,
thanks to the upgraded target system, a significant improvement in
luminosity and a wider choice of the target gas are expected.
The possibility of running with oxygen beams offers novel possibilities
for nuclear and astroparticle physics. In particular, collisions of O beams
on a hydrogen target can provide measurements of identified charged
particle production up to very forward rapidity in the O nucleus rest frame.

Speaker: Giacomo Graziani (INFN, Sezione di Firenze (IT))

LHCb_Smog2_graziani.pdf

Recording

17:25 → 17:40 Coffee break

17:40 → 18:30 Discussion

Conveners: Alice Ohlson (Lund University (SE)), Dr Guilherme Milhano (LIP-Lisbon & CERN TH), Yen-Jie Lee (Massachusetts Inst. of Technology (US))

17:40 Discussion on experimental opportunities

Speakers: Alice Ohlson (Lund University (SE)), Guilherme Milhano (LIP-Lisbon & CERN TH), Yen-Jie Lee (Massachusetts Inst. of Technology (US))

exp_discussion_ao_gm_yjl.pdf

Wednesday 10 February

14:30 → 15:50 pO for cosmic-ray physics

Convener: Lorenzo Bonechi (Istituto Nazionale di Fisica Nucleare (INFN))

14:30 LHCf achievements at pp and pPb

The aim of the LHC forward (LHCf) experiment is to provide critical data to test and tune hadronic interaction models used for very high energy cosmic-ay interactions. LHCf measures neutral particles, photons, neutrinos and pi0s, at very forward region of LHC collisions, and these energetic particles significantly contribute air shower development induced by cosmic-rays. LHCf had several operations with pp and pPb collisions during Run1 and Run2 and published several results. In this talk, we will discuss about these achievement as an introduction of the following talk focusing on pO.

Speakers: Hiroaki Menjo (Nagoya University (JP)), Hiroaki Menjo (Nagoya University (JP))

20200210_pOworkshop_menjo.pdf

Recording

14:45 LHCf motivations and prospects of p-O collisions

A proton-oxygen run at the LHC would be a unique opportunity to reproduce the collision of a cosmic ray with a light nucleus of the atmosphere. The LHCf experiment will have the possibility to perform direct measurements of the very-forward neutral particle production and the nuclear modification factor without the need of an interpolation of the results in proton-proton and proton-lead collisions. Another advantage of p-O collision is the much smaller contribution of Ultra Peripheral Collisions to the particle production with respect to the p-Pb case, which will lead to more precise measurements for the tuning of the phenomenological hadronic interaction models. LHCf will be able to operate both on the p-remnant and O-remnant side with a dedicated low-luminosity run. A common operation with the ATLAS ZDC is also under discussion.

Speaker: Alessio Tiberio (Universita e INFN, Firenze (IT))

Recording

tiberio_LHCf_pO_v2.pdf

15:10 Hadronic interactions and air showers : the need of Oxygen beam with LHCf

In detailed air shower simulations, the uncertainty in the prediction of shower observable for different primary particles and energies is currently dominated by differences between hadronic interaction models. With the general results of the first run of the LHC, the difference between post-LHC model predictions has been reduced at the same level than experimental uncertainties of cosmic ray experiments for Xmax measurements, but a deficit in muon production in simulation remains. At the same time new type of air shower observable, like the muon production depth, has been measured adding new constraints on hadronic models. Currently no model is able to reproduce consistently all mass composition measurement possible within the Pierre Auger Observatory for instance. In parallel, only few new measurements at LHC are providing new tests of the models which could help understanding the remaining differences between observed and simulated air showers. LHCf is the only LHC experiment testing the model used for such simulations in the relevant phase space and in combination with central trigger. The measurements in Run 1 and 2, already showed deficiency in the models. Results of LHCf with Oxygen beam which will include the nuclear effects missing in p-p collisions, as originally planed in Run 3, would be crucial to get enough information to solve the problems observed in a proper way and early enough that it can still be applied in the analysis of the current largest cosmic ray experiments.

Speaker: Dr Tanguy Pierog (KIT)

CR_LHCf_Pierog.pdf

Recording

15:50 → 16:15 Discussion

Conveners: Alessia Tricomi (Universita e INFN, Catania (IT)), David d'Enterria (CERN)

15:50 Discussion on forward physics and cosmic rays

Speakers: Alessia Tricomi (Universita e INFN, Catania (IT)), David d'Enterria (CERN)

Discussion_pO.pdf

16:15 → 16:30 Coffee break

16:30 → 17:10 Experimental opportunities with OO and pO

Convener: David Dobrigkeit Chinellato (University of Campinas UNICAMP (BR))

16:30 sPHENIX contribution

Speaker: Dennis Perepelitsa (University of Colorado Boulder)

dvp-sPHENIX-Opportunities-2-10-21.pdf

Recording

16:50 STAR contribution

Speaker: Wei Li (Rice University (US))

OOworkshop-weili-02102021v3.pdf

Recording

17:10 → 17:50 Soft dynamics of small systems

Convener: David Dobrigkeit Chinellato (University of Campinas UNICAMP (BR))

17:10 A Pythia/Angantyr perspective on OO and pO collisions

Speaker: Christian Bierlich (Lund University (SE))

cbierlich.pdf

Recording

17:50 → 18:15 Discussion

Conveners: Iurii Karpenko (SUBATECH Nantes), Prithwish Tribedy (Brookhaven National Lab), Raghav Kunnawalkam Elayavalli (Yale University)

17:50 Discussion on on Monte Carlo modelling and experimental opportunities at RHIC

Speakers: Iurii Karpenko (SUBATECH Nantes), Prithwish Tribedy (Brookhaven National Lab), Raghav Kunnawalkam Elayavalli (Yale University)

discussion_wednesday_evening.pdf

18:15 → 18:30 Coffee break

18:30 → 19:00 Discussion: Workshop summary

Conveners: Jasmine Therese Brewer (CERN), Dr Aleksas Mazeliauskas (CERN), Dr Wilke Van Der Schee (CERN)

18:30 Workshop summary

Speakers: Dr Aleksas Mazeliauskas (CERN), Jasmine Therese Brewer (CERN), Dr Wilke Van Der Schee (CERN)

OOSummaryDiscussion_v2.pdf

19:00 → 19:05 Closing