Connections between femtoscopy results in small and large systems

At the Large Hadron Collider nuclei are accelerated to speeds comparable to the speed of light. They are then collided and the resulting fireball quickly expands and is converted into thousands of particles. The LHC has the possibility to collide Pb ions and protons. A separate running mode enables asymmetric collisions of protons with Pb ions. A Pb ion, consisting of 208 nucleons can be considered “large” and a collision of two such ions produces a system which is at least an order of magnitude larger than its constituents. It is predicted that a new state of matter – Quark Gluon Plasma, consisting of deconfined quarks and gluons is created in such conditions. In contrast the collision of two protons is expected to be “small”. It is often treated as a “reference system”, where the creation of the QGP is not expected. However, this reasoning is based mostly on the expected size of the system created in pp collisions. It is therefore crucial to measure the size of both systems and confront it with the expectations. An intriguing question arises for p-Pb collisions, whether they should be treated as “small” or “large”. We shortly introduce the technique of femtoscopy, used to measure the size of the particle emitting system. We discuss its connection to the dynamics of the colllision evolution. We present recent femtoscopic results for pp, p-Pb and Pb-Pb collisions and discuss the similarities and differences observed.

[1]  R. Lednický Correlation femtoscopy , 2005, nucl-th/0510020.

[2]  B. Erazmus,et al.  Coulomb corrections for interferometry analysis of expanding hadron systems , 1998 .

[3]  Beam energy and centrality dependence of two-pion Bose-Einstein correlations at SPS energies / CERES Collaboration , 2002, nucl-ex/0207005.

[4]  S. H. Kim,et al.  Femtoscopy Of Pp Collisions At √s=0.9 And 7 Tev At The Lhc With Two-pion Bose-einstein Correlations , 2011 .

[5]  G. Goldhaber,et al.  Influence of Bose-Einstein Statistics on the Antiproton-Proton Annihilation Process , 1960 .

[6]  R. H. Brown,et al.  A Test of a New Type of Stellar Interferometer on Sirius , 1956, Nature.

[7]  Adam Kisiel,et al.  How to measure the size of the quark-gluon plasma? And why is it important? , 2015, Symposium on Photonics Applications in Astronomy, Communications, Industry, and High-Energy Physics Experiments (WILGA).

[8]  Y. Sinyukov,et al.  The HBT-interferometry of expanding sources , 1995 .

[9]  E. al.,et al.  Experimental and theoretical challenges in the search for the quark-gluon plasma: The STAR Collaboration's critical assessment of the evidence from RHIC collisions , 2005, nucl-ex/0501009.

[10]  C. Henderson,et al.  The PHOBOS Perspective on Discoveries at RHIC , 2005 .

[11]  A. Kisiel,et al.  Pion, kaon, and proton femtoscopy in Pb-Pb collisions at √{s NN }=2.76 TeV modeled in (3+1)D hydrodynamics , 2014, 1409.4571.

[12]  Quark gluon plasma and color glass condensate at RHIC? The Perspective from the BRAHMS experiment , 2005 .

[13]  E. al.,et al.  Formation of dense partonic matter in relativistic nucleus–nucleus collisions at RHIC: Experimental evaluation by the PHENIX Collaboration , 2004, nucl-ex/0410003.

[14]  M. Bowler Coulomb corrections to Bose-Einstein corrections have greatly exaggerated , 1991 .

[15]  A. Kisiel Signatures of collective flow in high multiplicity pp collisions , 2010, 1012.1517.

[16]  R. H. Brown,et al.  A New type of interferometer for use in radio astronomy , 1954 .

[17]  Matthias Rudolph Richter,et al.  Two-pion femtoscopy in p-Pb collisions at √sNN = 5.02 TeV , 2015 .

[18]  Jr.,et al.  Pion femtoscopy in p+p collisions at √s=200 GeV , 2010, 1004.0925.

[19]  J. G. Contreras,et al.  Two-pion Bose–Einstein correlations in central Pb–Pb collisions at =2.76 TeV , 2011 .