Origin of nuclear clusters in hadronic collisions

19 May 2020, 09:00 → 20 May 2020, 18:10 Europe/Zurich

Zoom only (CERN)

Alexander Philipp Kalweit (CERN), Kfir Blum (CERN), Laura Fabbietti (Technische Universität München), Maximiliano Puccio (CERN)

The goal of this mini-workshop is to solve the question of the origin of loosely-bound nuclei formed in hadronic collisions. This is a well defined question, the solution of which could shed light on the puzzling feature of seemingly thermal statistics in the yields of different hadrons at the LHC and other experiments. The main discussion is theoretical, but there will be strong interplay with experimentalists working on relevant analyses.

The format consists of invited talks, geared towards an audience of experts in the field, as well as working group discussions structured around a number of currently on-going analyses.

ZOOM connection is available here:

https://cern.zoom.us/j/92944591581

IMPORTANT NOTICE: Due to the COVID-19 situation, this meeting is now planned to take place ONLINE ONLY without physical presence at CERN. While we are still considering the logistical details, participants are requested to NOT purchase travel to CERN at this time.

Tuesday 19 May

1 Starting comments / EXP overview

Speaker: Alexander Philipp Kalweit (CERN)

ThInstituteAKAL.pdf

2 The thermal-statistical model applied to nuclear clusters

Speaker: Anton Andronic (Westfaelische Wilhelms-Universitaet Muenster (DE))

therm_frag.pdf

3 Coalescence as the origin of nuclear clusters

Measurements of the production of light nuclei in relativistic heavy-ion collisions present us with an apparent puzzle: While the momentum spectra of these nuclei indicate a low "kinetic freeze-out” temperature coupled with strong collective flow, their yields reflect a much higher “chemical freeze-out” temperature, consistent with the quark-gluon plasma hadronization temperature. How can these fragile nuclei “survive” the rescattering in the hadronic phase, cooling down in the process and picking up additional collective flow, without getting destroyed and depleted? I will explain how the coalescence model reconciles these observations and how recent kinetic simulations of the process support this model.

Speaker: Ulrich Heinz (The Ohio State University)

NuclearClusters_2020_Heinz.pdf

12:00 Lunch Break

4 Light-nuclei production: experimental measurements vs theoretical predictions

An abundant production of light nuclei and anti-nuclei have been observed in hadron collisions for a long time. However, their production mechanisms are still not completely understood. In this presentation, the experimental results about the production of light (anti-)nuclei in different collision systems and at different energies will be compared with the predictions of the coalescence model and of the statistical hadronisation model.

Speaker: Luca Barioglio (Universita e INFN Torino (IT))

Light_nuclei_Barioglio.pdf

5 Coalescence--correlations relation: B2 vs. HBT/radii

Discussion of the EXP effort to test the predicted relation between pair correlations and coalescence yield. Main questions for TH and for the analysis, results and discussion.

Speakers: Bernhard Hohlweger (TUM), Bernhard Hohlweger (Technische Universitaet Muenchen (DE))

200518_Coalescence_upload.pdf

6 Discussion: coalescence vs. HBT

16:00 Break

7 Nuclear clusters in an off-equilibrium thermal model

The production of light (anti-)(hyper-)nuclei during the hadronic phase of heavy-ion collisions at the LHC is discussed in the framework of an extended thermal model approach — the Saha equation —making use of an analogy between the evolution of the early universe after the Big Bang and that of "Little Bangs" created in the lab. Then rate equations are utilized to relax the assumption of relative chemical equilibrium of nuclear reactions, revealing only moderate deviations from the Saha equation baseline.

Speaker: Dr Volodymyr Vovchenko (Lawrence Berkeley National Laboratory)

Vovchenko_NuclearClusters_2020.pdf

8 Cluster formation in a transport model

Speakers: Dmytro Oliinychenko, Dr Dmytro Oliinychenko (Lawrence Berkeley National Laboratory)

Oliinychenko_CERN_May2020.pdf

9 Google Doc Discussion

Wednesday 20 May

10 Hypertriton structure

Speaker: Hans-Werner Hammer

HammerHypertriton.pdf

11 Hypertriton lifetime

Speaker: Jean-Marc Richard (IP2I, Lyon)

ALICE-JMR-05-2020.pdf

12 Hypertriton yield at ALICE: EXP vs. TH

Speakers: Maximiliano Puccio (CERN), Maximiliano Puccio

200520-mpuccio-hypertriton.pdf

13 Discussion: Hypertriton as a probe of cluster formation

14 How to distinguish coalescence from thermal production of light nuclei

There are discussed two methods to distinguish the coalescence from thermal production of light nuclei. At first the hadron-deuteron correlation function is shown to carry information about an origin of deuterons, whether they are emitted from a fireball together with all other hadrons or formed due to final state interactions after nucleons left the fireball. Secondly, it is proposed to measure the yield of an exotic nuclide $^{4}$Li and compare it the yield of $^{4}$He. The coalescence and thermal models predict a significantly different ratio of the yields of $^{4}$Li to $^{4}$He. A measurement of $^{4}$Li is discussed.

Speakers: Stanislaw Mrowczynski (Jan Kochanowski University), Stanislaw Mrowczynski

Mrowczynski-Origin-of-Nuclear-Clusters-2020.pdf

There are discussed two methods to distinguish the coalescence from thermal production of light nuclei. At first the hadron-deuteron correlation function is shown to carry information about an origin of deuterons, whether they are emitted from a fireball together with all other hadrons or formed due to final state interactions after nucleons left the fireball. Secondly, it is proposed to measure the yield of an exotic nuclide ⁴Li and compare it the yield of ⁴He. The coalescence and thermal models predict a significantly different ratio of the yields of ⁴Li to ⁴He. A measurement of ⁴Li is discussed.

12:00 Break

15 Google Doc Discussion & Workshop summary

clusters 2020 CERN.pdf

16 TH Colloquium: Jesse Thaler (https://indico.cern.ch/event/888504/)