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Multiquark hadrons from Heavy Ion Collisions New Frontiers in QCD 27-28 October 2011 Yonsei University Sungtae Cho Institute of Physics and Applied Physics Yonsei University

− This talk is based on Identifying Multiquark Hadrons from Heavy Ion Collisions, ExHIC Collaboration, Phys. Rev. Lett. 106 , 212001 (2011) Studying Exotic Hadrons In Heavy Ion Collisions, ExHIC Collaboration, arXiv: 1107.1302 27-28 October 2011 New Frontiers in QCD 2 Yonsei Univ.

Outline − Introduction − The statistical model − Hadronization in heavy ion collisions − The coalescence model − Results − Conclusion 27-28 October 2011 New Frontiers in QCD 3 Yonsei Univ.

Introduction − Normal hadrons : Mesons and Baryons − Multiquark hadrons i) H dibaryon and scalar tetra quark (1976) f ( 980 ) 0 hadronic molecule (1990) K K ii) Hadronic molecules & multiquark states Belle (2003) X ( 3872 ) BaBar (2003) D ( 2317 ) sJ 27-28 October 2011 New Frontiers in QCD 4 Yonsei Univ.

Introduction − Normal hadrons : Mesons and Baryons − Multiquark hadrons i) H dibaryon and scalar tetra quark (1976) f ( 980 ) 0 hadronic molecule (1990) K K ii) Hadronic molecules & multiquark states  Belle (2003) * * D D , D D , q q c c X ( 3872 )  BaBar (2003) DK , c s , q q c s D ( 2317 ) sJ 27-28 October 2011 New Frontiers in QCD 5 Yonsei Univ.

− The purpose of this work i) To estimate the possibility of observing predicted exotics with/without heavy quarks in heavy ion collision experiment ii) To find a possible solution to a problem of identifying hadronic molecular states and/or hadrons with multiquark components − We focus on hadron production yields i) Normal hadron (light quark hadrons) production yields are well described by the statistical model ii) Many aspects of the heavy ion collision experimental results can nicely be explained by the coalescence model 27-28 October 2011 New Frontiers in QCD 6 Yonsei Univ.

The statistical model − Hadron yield ratios at RHIC A. Andronic, P. Braun-Munzinger, and J. Stachel, Nucl. Phys. A 772 , 167 (2006) 27-28 October 2011 New Frontiers in QCD 7 Yonsei Univ.

− The thermally equilibrated system  2 g p dp     i 2 2 N V E m p     i H 2 1 E i T / i i i 2 e 1 H i 0          n n n n e c c B B s s Fugacity c i) The hadronization temperature and the chemical potential are determined from the experimental data ii) We expect the statistical model to play its important role again in describing the expected multiquark hadron yields produced at heavy ion collision experiment 27-28 October 2011 New Frontiers in QCD 8 Yonsei Univ.

Hadronization in heavy ion collisions − The fragmentation picture i) A parton spectrum relates the probability for a parton to hadronize into a hadron, carrying a fraction z<1 of the momentum of the parent parton. ii) The puzzle in antiproton /pion ratio Requires a rescaling for a fraction z for all hadrons V. Greco, C. M. Ko, and P. Levai, Phys. Rev. Lett. 90 , 202302 (2003) 27-28 October 2011 New Frontiers in QCD 9 Yonsei Univ.

− Coalescence vs. fragmentation i) There must be a competition : A fragmentation dominates at large transverse momenta and a coalescence prevails at lower transverse momenta h h p p   Coal Frag T T vs. p p T T n z − The coalescence picture i) The quark number scaling of the elliptic flow of identified hadrons ii) The yield of antihyperons recently discovered in heavy ion collision at RHIC 27-28 October 2011 New Frontiers in QCD 10 Yonsei Univ.

The coalescence model − Yields of hadrons with n constituents     3 n 1 p d d p    Coal W i i i     ( , ) ( , , : , , ) N g f x p f x x p p  i i 1 n 1 n 3   g ( 2 ) E  i 1 i i i) Wigner function : Coalescence probability function W   f ( x , , x : p , , p ) 1 1 n n     n y y y y             p y * 1  1  n n dy e x , , x x , , x i i i 1 n 1 n     2 2 2 2  i 1 ii) Covariant phase space density 3 d p     i p d f ( x , p ) N  i i i i i 3 ( 2 ) E 27-28 October 2011 i New Frontiers in QCD 11 Yonsei Univ.

− The coalescence model can i) explain both the quark and hadron coalescence        N Coal W    g f ( x , , x : p , , p ) 1 n 1 n   27-28 October 2011 New Frontiers in QCD 12 Yonsei Univ.

− The coalescence model can i) explain both the quark and hadron coalescence  c c       N Coal W    g f ( x , , x : p , , p ) q q c c 1 n 1 n   X ( 3872 ) * D D 27-28 October 2011 New Frontiers in QCD 13 Yonsei Univ.

− The coalescence model can i) explain both the quark and hadron coalescence  c c       N Coal W    g f ( x , , x : p , , p ) q q c c 1 n 1 n   X ( 3872 ) * D D ii) consider the internal structure of hadrons  2 3 / 2 N ( 4 ) i i ~ 0 . 360    2 g V ( 1 2 T ) i i i      2 3 / 2 2 N ( 4 ) 2 2 T i i i i   ~ 0 . 093       2 2   g V ( 1 2 T ) 3 ( 1 2 T ) i i i i i 2      2 3 / 2 2 N ( 4 ) 8 2 T i i i i   ~ 0 . 029       2 2   g V ( 1 2 T ) 15 ( 1 2 T ) 27-28 October 2011 i i i i i New Frontiers in QCD 14 Yonsei Univ.

− Final results l       i 2 3 / 2 2 n n 1 ( 4 ) ( 2 )! ! 2 N l T    Coal i i i i i   N g        h 2 2   g V ( 1 2 T ) ( 2 l 1 )! ! ( 1 2 T )   j 1 i 1 i i i i i i 1 1 1 1     i    i  m  i i 1 m i j j − The quark coalescence   : Reference hadrons - ( 2286 ) ( 1115 ), c − The hadron coalescence : The relation between the binding energy and the root mean square radius 3 2  2 a     2 0 B . E . r  2  2 2 r 2 a 2 0 27-28 October 2011 New Frontiers in QCD 15 Yonsei Univ.

Results − Summary of multiquark hadrons considered 27-28 October 2011 New Frontiers in QCD 16 Yonsei Univ.

− Estimated multiquark hadron yields at RHIC and LHC 27-28 October 2011 New Frontiers in QCD 17 Yonsei Univ.

− The loosely bound exotic hadron molecules are more produced Coal N , 2  i molecule Stat N i − Normal hadron zone Coal N   i , normal 0 . 2 2 Stat N i − The exotic multiquark hadrons become suppressed Coal N  i , multiquark 0 . 2 Stat N 27-28 October 2011 New Frontiers in QCD 18 i Yonsei Univ.

− Comparison to experimental data i) Fortunately, STAR Collaboration has a preliminary measurement for P. Fachini [STAR Collaboration], Nucl. Phys. A 715 , 462 (2003) f ( 980 ) 0 N f ( 980 ) 0 ~ 0 . 2 N  0 ii) Can we say whether is a tetraquark f ( 980 ) 0 hadron or a hadronic molecule? K K : QWG2011, 8th International 4-7 October 2011 GSI 19 Workshop on Heavy Quarkonium

− Comparison to experimental data i) Fortunately, STAR Collaboration has a preliminary measurement for P. Fachini [STAR Collaboration], Nucl. Phys. A 715 , 462 (2003) f ( 980 ) 0 N f ( 980 ) 0 ~ 0 . 2 N   0 ii) Can we say whether is a tetraquark f ( 980 ) 0 hadron or a hadronic molecule? K K : At least, must f ( 980 ) 0 not be a tetraquark hadron   N 8 f ( 980 ) QWG2011, 8th International 4-7 October 2011 GSI 20 Workshop on Heavy Quarkonium

Conclusion − Exotic hadrons in relativistic heavy ion collisions i) The yields of exotic hadrons are large enough to be measurable in experiments : Relativistic heavy ion collisions can provide an opportunity to search for exotic hadrons ii) The probability to combine n quarks into a compact region is suppressed as n increases iii) The yield of a hadron in relativistic heavy ion collision reflects its structure : Therefore, yields can be used to discriminate the different pictures for the structure of exotic hadrons 27-28 October 2011 New Frontiers in QCD 21 Yonsei Univ.

Backup slides 27-28 October 2011 New Frontiers in QCD 22 Yonsei Univ.

− Time evolution of quark -gluon plasma   t  2 2 z J. D. Bjorken, Phys. Rev. D 27 , 140 (1983) i) Collision ii) Pre-equilibrium : QGP iii) Hadronization : Mixed phase iv) Freeze-out : Hadron gas 27-28 October 2011 New Frontiers in QCD 23 Yonsei Univ.