1. Possible structures of a neutron star Exploring dense nuclear matter The Compressed Baryonic Matter Experiment CBM@FAIR atom: 10 -10 m nucleus: 10 -14 mnucleon: 10 -15 m quark: <10 -18 m Until the beginning of the 20th century people believed that atoms are the elementary building blocks of matter. Since then we have learnt that atoms have a substructure: Each atom consists of a nucleus with electrons orbiting around. The nucleus itself is composed of protons and neutrons which, on their part, consist of 3 fundamental particles, the so-called quarks. Quarks never appear alone, they are glued together by "gluons", particles which represent the strong force. The structure of matter The CBM collaboration: 47 institutions, > 400 members Croatia: RBI, Zagreb Split Univ. China: CCNU Wuhan Tsinghua Univ. USTC Hefei Czech Republic: CAS, Rez Techn. Univ.Prague France: IPHC Strasbourg Hungaria: KFKI Budapest Budapest Univ. Norway: Univ. Bergen Germany: Frankfurt Univ. IKF Frankfurt Univ. FIAS GSI Darmstadt Giessen Univ. Heidelberg Univ. P.I. Heidelberg Univ. KIP Heidelberg Univ. ZITI HZ Dresden- Rossendorf Münster Univ. Tübingen Univ. Wuppertal Univ. Korea: Korea Univ. Seoul Pusan Nat. Univ. Romania: NIPNE Bucharest Univ. BucharestIndia: Aligarh Muslim Univ. Panjab Univ. Rajasthan Univ. Univ. of Jammu Univ. of Kashmir Univ. of Calcutta B.H. Univ. Varanasi VECC Kolkata SAHA Kolkata IOP Bhubaneswar IIT Kharagpur Gauhati Univ. Poland: AGH Krakow Jag. Univ. Krakow Silesia Univ. Katowice Warsaw Univ. Russia: IHEP Protvino INR Troitzk ITEP Moscow KRI, St. Petersburg Kurchatov Inst., Moscow LHEP, JINR Dubna LIT, JINR Dubna MEPHI Moscow Obninsk State Univ. PNPI Gatchina SINP MSU, Moscow St. Petersburg P. Univ.Ukraine: T. Shevchenko Univ. Kiev Kiev Inst. Nucl. Research In the laboratory different phases of nuclear matter can be produced by colliding two heavy nuclei at almost the speed of light. In the center of these collisions a transient state of matter is created where densities are as high as in supernova explosions or neutron stars and where temperatures are much higher than in the sun. The energy released from this "fireball" is converted into more than 1000 new particles which the CBM experiment is able to measure. These particles are used as diagnostic tools for studying the dense and hot nuclear matter created in nucleus-nucleus collisions. Dense nuclear matter in the laboratory Layouts of the CBM experiment UrQMD simulation U+U 23 A GeV compression The phase diagram of strongly interacting matter heat Much like the different phases of water (ice – liquid – gas), various phases of nuclear matter can be formed by compressing or heating atomic nuclei: Protons and neutrons melt in a "soup" of quarks and gluons. Free floating quarks and gluons constitute then a new phase of nuclear matter: the "quark-gluon plasma". Phases of nuclear matter Scientists expect that a quark-gluon plasma was the initial state of matter in the early universe, microseconds after the big bang and right before any atomic matter was formed. In today's universe these "dense plasmas" are expected to exist e.g. within the cores of neutron stars.