Femtoscopy of proton-proton collisions in the ALICE experiment DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Nicolas Bock, B.Sc. B.Eng., M.Sc. Graduate Program in Physics The Ohio State University 2011 Dissertation Committee: Professor Thomas J. Humanic, Advisor Professor Michael Lisa #1 Professor Klaus Honscheid #2 Professor Richard Furnstahl #3 c Copyright by Nicolas Bock 2011 Abstract The Large Ion Collider Experiment (ALICE) at CERN has been designed to study matter at extreme conditions of temperature and pressure, with the long term goal of observing deconfined matter (free quarks and gluons), study its properties and learn more details about the phase diagram of nuclear matter. The ALICE experiment provides excellent particle tracking capabilities in high multiplicity proton-proton and heavy ion collisions, allowing to carry out detailed research of nuclear matter. This dissertation presents the study of the space time structure of the particle emission region, also known as femtoscopy, in proton- proton collisions at 0.9, 2.76 and 7.0 TeV. The emission region can be characterized by taking advantage of the Bose-Einstein effect for identical particles, which causes an enhancement of produced identical pairs at low relative momentum. The geometry of the emission region is related to the relative momentum distribution of all pairs by the Fourier transform of the source function, therefore the measurement of the final relative momentum distribution allows to extract the initial space-time characteristics. Results show that there is a clear dependence of the femtoscopic radii on event multiplicity as well as transverse momentum, a signature of the transition of nuclear matter into its fundamental components and also of strong interaction among these. The present work also considers a physics motivated parametrization of non-femtoscopic correlations to characterize the background signal. It is shown that at these high energies and multiplicities this parametrization does not work as it does for lower energies. A special chapter containing the detailed study of possible signatures of black hole formation is also presented. ii Acknowledgments I would like to thank my advisor Dr. Tom Humanic for all your support and guidance during these Ph.D. years, it has been a great pleasure to learn from you and work with you in such a great project as is the ALICE experiment at CERN. Too bad we did not detect any black holes, but maybe at 14 TeV. Thank you also for all your encouragement to advance my career at conferences and workshops. My co-advisor Dr. Mike Lisa: It was always very enlightening to go to your office and show you results or even code as you always had an answer to my questions. The Experimental Heavy Ion Group at Ohio State: Chris Anson, Zibi Chajecki, Dave Truesdale, Matt Steinpreis. The Femtoscopy Group at CERN: Adam Kisiel, Dariusz Miskowiec, Sebastian Huber, Jorge Mercado, Johanna Gramling, and Mads Stormo Nielsen. My Collaborators and friends at ALICE and CERN: Mario Sitta, Francesco Prino, Dhe- van Ghandagaran, Lucy Renshall, Carnita Hervet, Ulla Tihinen, Bjorn Nielsen, Emmanuelle Biolcati and Stephania Beole. I would also like to thank all the professors at OSU that contributed in one way or another to my formation as a physicist: (in no particular order): Dr. David Stroud, Dr. Eric Braaten, Dr. John Beacom, Dr. Junko Shigemitsu, Dr. Dick Furnstahl, Dr. Ulrich Heinz, Dr. Klaus Honscheid, Dr. Yuri Kovchegov, Dr. Julia Meyer, Dr. Samir Matur. Many thanks to the OSU Physics Department staff with whom I interacted on many occasions: Mary Kay Jackson, Arnay Tate, Beth Deinlein, Brenda Mellet, Karen Kitts, Yavonne McGarry. I wish acknowledge the support of the U.S. National Science Foundation under grant PHY-0970048, and to acknowledge computing support from the Ohio Supercomputing Cen- ter. I would like to thank the Physics Department at OSU for the continued support and the great opportunity of becoming a PhD here. I enjoyed and learned a lot from all the classes I took, and the experience as a Teaching Associate was also very rewarding. Finally I wish to thank my family for their constant support. iii Vita April 10, 1979 . Born| Bogot´a,Colombia January 2002 - September 2004 . Undergraduate Teaching Associate, Uni- versidad de los Andes, Bogot´aColombia September 18, 2004 . B.S. Physics, Universidad de los Andes, Bogot´aColombia September 18, 2004 . B.S. Mechanical Engineering, Universidad de los Andes, Bogot´aColombia January 2005 - July 2006 . Adjunct Faculty Professor, Universidad Javeriana, Bogot´aColombia January 2006 - July 2006 . Adjunct Faculty Professor, Universidad del Bosque, Bogot´aColombia September 2006 - August 2009 . Graduate Teaching Associate, The Ohio State University, Columbus Ohio August 31, 2009 . M.S. Physics, The Ohio State University, Columbus, Ohio September 2009 - August 2011 . Graduate Research Associate, The Ohio State University, Columbus Ohio Publications in refereed journals 1. Nicolas Bock for the ALICE Collaboration, Femtoscopy and energy-momentum con- servation effects in proton-proton collisions at 900 GeV in ALICE. Workshop for young scientists on the physics of ultra-relativistic heavy ion collisions, June 21 -26, La Londe Les Maures, France. 2011 J. Phys.: Conf. Ser. 270 012022, arXiv:1009.3157v1 [hep-ex]. 2. Nicolas Bock, Thomas J. Humanic, Quantitative Calculations for Black Hole Pro- duction at the Large Hadron Collider, Int.J.Mod.Phys.A24:1105-1118,2009. iv 3. B Alessandro et al, Operation and calibration of the Silicon Drift Detectors of the ALICE experiment during the 2008 cosmic ray data taking period, 2010 JINST 5 P04004 Conference Proceedings 1. Nicolas Bock, Energy momentum conservation effects on two-particle correlation func- tions. VI Workshop on Particle Correlations and Femtoscopy, September 14-17, 2010, Kiev, Ukraine. arXiv:1101.5241v1 [hep-ex] (2010). Submitted to Physics of Elementary Particles and Atomic Nuclei, Letters. Publications with the ALICE Collaboration 1. The ALICE Collaboration, Two-pion Bose-Einstein correlations in pp collisions at p s 900 GeV at the LHC, Phys. Rev. D 82, 052001 (2010) p 2. The ALICE Collaboration, Femtoscopy of pp collisions at s=0.9 and 7 TeV at the LHC with two-pion Bose-Einstein correlations, arXiv:1101.3665v1 [hep-ex], To be published in Physical Review C. 3. The ALICE Collaboration, Two-pion Bose-Einstein correlations in central PbPb col- p lisions at (sNN ) = 2.76 TeV ALICE Collaboration, Phys.Lett.B 696:328-337 2011, arXiv:1012.4035v2 [nucl-ex]. Invited Presentations 1. HBT Interferometry with the ALICE experiment 26th Lake Louise Winter Institute, Lake Louise, Canada. Feb 20-26, 2011 2. Energy-momentum conservation effects on the two-particle correlation function VI. Workshop on Particle Correlations and Femtoscopy, Bogolyubov institute for the- oretical physics Kiev, Ukraine. Sep 14 -18, 2010 v 3. Femtoscopy and energy-momentum conservation effects in ALICE Hot Quarks: Physics of ultra relativistic nucleus-nucleus collisions, La Londe Les Maures, France. June 21 - 27 2010 4. Improving femtoscopy by characterizing energy-momentum conservation effects Hayes Graduate Research Forum, The Ohio State University, Columbus Ohio. May 1 2010 5. Two pion femtosopy at 7 and 14 TeV pp collisions V. Workshop on Particle Correlations and Femtoscopy, CERN, Geneva, Switzerland. October 14 -17 2009. Full List of Publications with the ALICE Collaboration 1. The ALICE Collaboration, Higher harmonic anisotropic flow measurements of charged particles in Pb-Pb collisions at 2.76 TeV, arXiv:1105.3865v1 [nucl-ex], To be pub- lished in Physical Review Letters 2. The ALICE Collaboration, Production of pions, kaons and protons in pp collisions at p s= 900 GeV with ALICE at the LHC, Eur.Phys.J.C 71(6): 1655, 2011 3. The ALICE Collaboration, Rapidity and transverse momentum dependence of inclu- p sive J/psi production in pp collisions at s=7 TeV, arXiv:1105.0380v1 [hep-ex], To be published in Phys. Lett. B 4. The ALICE Collaboration, Strange particle production in proton-proton collisions at p s = 0.9 TeV with ALICE at the LHC, Eur. Phys. J. C 71 (3), 1594 (2011) 5. The ALICE Collaboration, Centrality dependence of the charged-particle multiplicity p density at mid-rapidity in Pb-Pb collisions at sNN = 2.76 TeV, Phys. Rev. Lett. 106, 032301 (2011) 6. The ALICE Collaboration, Suppression of Charged Particle Production at Large p Transverse Momentum in Central Pb-Pb Collisions at sNN = 2.76 TeV, Phys. Lett. B 696 (2011) 30-39 vi 7. The ALICE Collaboration, Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV, Phys. Rev. Lett. 105, 252302 (2010) 8. The ALICE Collaboration, Charged-particle multiplicity density at mid-rapidity in p central Pb-Pb collisions at sNN = 2.76 TeV, Phys. Rev. Lett. 105, 252301 (2010) 9. The ALICE Collaboration, Transverse momentum spectra of charged particles in pro- p tonproton collisions at s=900 GeV with ALICE at the LHC, Physics Letters B 693 (2010) 5368 10. The ALICE Collaboration, Midrapidity Antiproton-to-Proton Ratio in pp Collisons p at s=0.9 and 7 TeV Measured by the ALICE Experiment, Phys Rev Lett Vol.105, No.7, (2010) 11. The ALICE Collaboration, Charged-particle multiplicity measurement in protonproton p collisions at s=7 TeV with ALICE at LHC, Eur. Phys. J. C (2010) 68: 345354 12. The ALICE Collaboration, Charged-particle multiplicity measurement in protonproton p collisions at s=0.9 and 2.36 TeV with ALICE at LHC, Eur. Phys. J. C (2010) 68: 89108 13. The ALICE Collaboration, Alignment of the ALICE Inner Tracking System with cosmic-ray tracks, J. Instrum. 5, P03003 14. The ALICE Collaboration, First protonproton collisions at the LHC as observed with the ALICE detector: measurement of the charged-particle pseudorapidity density at p s=900 GeV, Eur.