Short Description of ReteQuarkonii activities

Between 1 nanosecond and 1 micro-second after the Big-Bang the temperature of the universe was above 175 MeV (~ K) and the baryonic density was around zero (almost the same amount of matter and antimatter), at this moment, the Quark-Gluon Plasma (QGP) was the supposed main state of matter [1]. Today, matter in the Universe is structured by quarks and gluons bound into proton and neutrons due to the strong interaction. The QGP is a deconfined state of matter where quarks and gluons are not bound into nucleons. The figure 1 illustrates the evolution of the universe from Big-Bang up to today, where, just after the Big-Bang the QGP phase is illustrated. After this phase, the universe gets colder and first nucleons are structured. On this picture, one should be careful with illustrations that have different scales in nature.


big-bang.png

The conditions required to produce such a deconfined state of matter can be reached in ultra relativistic heavy ion collisions, where 2 heavy ions beams (gold, lead, indium, …) are accelerated at speed close to the speed of lights. The energy reached in such ultra relativistic heavy ion collisions allows the production of QGP during several tens of fm/c (~ s). The figure 2 is a schematic view of the phase diagram of the the hadronic matter. A phase diagram illustrates the different states a matter can probed. For example, on the phase diagram of water, you will find for different conditions of pressure and temperature, the states of gas, liquid water and ice. Analogically, hadronic matter exhibits different states depending on the pressure and temperature conditions, like hadron gas, color superconductor quark matter and the quark gluon plasma. This is illustrated on the figure 2. On this picture, the transition between hadrons gas and QGP is shown by the red line. This red line was crossed by different experiments around different particles accelerators, such as SPS (Super Proton Synchrotron), RHIC (Relativistic Heavy Ion Collider) and LHC (Large Hadron Collider).


Hadronic_phase_diagram.jpg

To test whether QGP was formed or not in collisions, it is needed to look at several measurements, several observables. ReteqQuakonii activities are focused on one particular type of observables: Quarkonia. Quarkonia are bound state of pairs, where is a heavy quark, a charm quark ( ) or a beauty quark ( ). Their study is fundamental for the comprehension of the nuclear matter and the quark-gluon plasma. In 1986 Matsui and Satz predicted an anomalous suppression of the J/Ψ particle ( ) in central heavy ion collisions [2]. A normal suppression is observed in heavy ion collision without QGP due to the presence of nuclear matter. This is called the cold nuclear matter effect. If a QGP is formed, due to color screening in the hot medium, the J/Ψ should be dissociated. This is called hot nuclear matter effect as it is illustrated on the picture 2. If a QGP is formed, the pair melts into the medium. In addition to this suppression mechanism, theoretical predictions based on recombination models account for an enhancement of J/ Ψ production due to regeneration in the medium. More explanation can be found on [3]. Those phenomena will be studied at LHC.


JPsi_suppression.jpg

The Retequarkonii network concerns 28 laboratories from Europe with teams working on Quarkonia physics in different international experiments such as ALICE and CMS at LHC. It is structured in 5 working groups each one focused on a specific subject on Quarkonia physics in heavy ion collision and pp collisions. The first one is “Open Heavy flavors” which focuses on the experimental measurement of total production cross section of charm and beauty, reference for Quarkonia nuclear effects and contribution to B decays in the charmonium production yields. The second one is “Soft and hard diffraction at LHC” which look at the Quarkonia production from photon and pomeron interactions. Then we have the “Cold nuclear matter effects” group and the “Hot nuclear matter effect” group working on the effect on Quarkonia production from nuclear matter. Finally, the last working group is working on a database project for Quarkonia results. All the details information can be found on the TWiki page of the network [4]. We use the website as an interface to communicate and report on the advancement of our activities.

For the study of Quarkonia production in heavy ion and proton-proton collisions it is needed to do ratios of spectrum, to compare spectrum at different energies, from different initial states. In the J/ Ψ production, to disentangle the anomalous from the normal suppression, it is necessary to constrain well the models that describe cold nuclear matter effect. Finally, for the study of Quarkonia physics, it is necessary to have a complete overview of all existing data. It is the motivation for the creation of a Quarkonia database that contains all published results on Quarkonia physics in hadronic collisions. This work is done in collaboration with HEDPATA, the Durham database for high energy physic. Quarkonia related references are including in the database and a dedicated webpage was created as a review of Quarkonia physic where all data are directly accessible [5]. A screenshot of this webpage is presented on figure 4.


webpage.png

The Retequarkonii network aims at organizing different meetings and conferences. The first one we organized was the “ReteQuarkonii Thematic Day”, on the 09th of February 2010, just after the first LHC collisions at the end of December at 900GeV and 2.36TeV. It was a one-day workshop on Quarkonium production at the LHC that aims to promote rich discussion between theorists and experimentalists, with talks from theorists and first results from the four LHC experiments. It was organized at IPN Orsay by a sub-group of members of the ReteQuarkonii network. All information about this workshop can be found on [6]. In the continuity, RQW2010 (First ReteQuarkonii Workshop) was organized in Nantes from 25 to 28 October. It leads to intense discussion between experimentalist and theorists during one week. The workshop was divided into session, related to the 5 working groups of the network. Picture taken during the workshop can be found on [7].

With a strong motivation for the formation of young scientists, the ReteQuarkonii network also organized two schools, dedicated to students and post-doc. The first one "Diffractive and electromagnetic processes at high energies", was held on september 6-10 2010 at Acquafredda, Italy. Another international school was organized in Torino from 7 to 12 March 2011 on “Quark-Gluon Plasma and Heavy Ion Collisions: past, present, future”. In the meantime the network gave two one-year post-doc grants. The first one concerned Sarah Porteboeuf, she did a one-year post doc at LLR laboratory, working half time on the Quarkonia database project. At the end of her post-doctoral position, she got a permanent position at LPC laboratory. The second one has been provided by Loïc Manceau since February 2011 at INFN-Torino.

[1] P. Braun-Munzinger and J. Stachel, Nature 448, 302 (2007); e-Print: arXiv : 1101.3167 [nucl-th] (2011)

[2] T. Matsui and H. Satz, Phys. Lett. B178, 416 (1986)

[3] http://aliceinfo.cern.ch/Public/Welcome.html, http://www.bnl.gov/rhic/physics.asp

[4] https://twiki.cern.ch/twiki/bin/view/ReteQuarkonii

[5] http://hepdata.cedar.ac.uk/review/quarkonii/

[6] http://indico.cern.ch/conferenceDisplay.py?confId=80227

[7] http://indico.cern.ch/conferenceDisplay.py?ovw=True&confId=93174, http://laurent.aphecetche.fr/cern/rqw2010/

Contact Person : Sarah Porteboeuf (sarah.porteboeuf@clermontNOSPAMPLEASE.in2p3.fr)

PDF Printable version Short_report_on_ReteQuarkonii_Activity_2.pdf


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-- SarahPorteboeuf - 15-Mar-2011

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