NEW RESULTS FROM THE ALICE EXPERIMENT University of Birmingham O. - PowerPoint PPT Presentation

NEW RESULTS FROM THE ALICE EXPERIMENT University of Birmingham O. Villalobos Baillie September 26th 2012 University of Birmingham

Plan of Talk • Introduction • QGP properties • ALICE Detector • Reminder Slides often “stolen” from Quark • System Size Matter 2012. • Radial and Elliptic Flow • Jet Quenching • New Results • Future Plans • Summary September 26th 2012 2 O. Villalobos Baillie -University of Birmingham

INTRODUCTION O. Villalobos Baillie -University of September 26th 2012 3 Birmingham

Early Ideas • It was realized fairly early in the development of Quantum Chromodynamics that at sufficiently extreme conditions, quarks and gluons would become deconfined. Two papers appeared on this topic in 1975. PRL 34 (1975) 1353 September 26th 2012 4 O. Villalobos Baillie -University of Birmingham

Early Ideas PLB59B (1975) 67 September 26th 2012 5 O. Villalobos Baillie -University of Birmingham

Early Ideas N. Cabibbo and G. Parisi PL 59B (1975) 67 September 26th 2012 6 O. Villalobos Baillie -University of Birmingham

Quark-Gluon Plasma • At high temperature, or at high net baryon density, QCD indicates that matter undergoes a phase transition to a phase in which quarks and gluons can move freely (QGP). • Lattice QCD indicates that a fairly rapid transition occurs, which does not appear to be first order for ρ 0 ~0. • Lattice calculations also show plateau comes about 15% below Stefan-Boltzmann limit – QGP does not behave like an ideal gas. • Current estimates are that phase transition occurs for T~170 MeV and ϵ ~1 GeV fm -3 September 26th 2012 7 O. Villalobos Baillie -University of Birmingham

Observables Jets 8 O. Villalobos Baillie -University of September 26th 2012 Open charm, beauty 8 Birmingham

What is “extreme”? • T of 170 MeV corresponds (in Kelvin) to around 2 × 10 12 K (10 5 times hotter than sun). • Heavy ion QGPs created at the LHC are estimated to reach an energy density ϵ ~ 5 GeV fm -3 , well above the transition temperature. • EXAMPLE Given that the annual energy consumption of the U.S. is about 10 17 BTU, how much QGP would we need to hold this amount of energy? September 26th 2012 9 O. Villalobos Baillie -University of Birmingham

Extreme conditions! • 10 17 BTU = 6.6 × 10 29 GeV , so this fits in a cube of size × 29 3 6.6 10 = × = µ Human Hair 9 5.09 10 fm 5.09 m 5 September 26th 2012 10 O. Villalobos Baillie -University of Birmingham

ALICE • The ALICE collaboration (A Large Ion Collider Experiment) is dedicated principally to the study of heavy ion collisions. • The design of the detector is strongly based on tracking , and aims to be able to track and identify charged particles even in central ion- ion collisions. • (dN/dy thought to be ~8000 at time design was made.) • Also electromagnetic calorimetry September 26th 2012 11 O. Villalobos Baillie -University of Birmingham

ALICE Technologies:18 Tracking: 7 Detector: PID: 6 Size : 16 x 26 meters O. Villalobos Baillie -University of 12 September 26th 2012 12 Birmingham Weight : 10,000 tons Calo.: 5

ALICE Technologies:18 Tracking: 7 Detector: PID: 6 Size : 16 x 26 meters O. Villalobos Baillie -University of 13 September 26th 2012 13 Birmingham Weight : 10,000 tons Calo.: 5

ALICE Technologies:18 Tracking: 7 Detector: PID: 6 Size : 16 x 26 meters O. Villalobos Baillie -University of 14 September 26th 2012 14 Birmingham Weight : 10,000 tons Calo.: 5

ALICE Technologies:18 Tracking: 7 Detector: PID: 6 Size : 16 x 26 meters O. Villalobos Baillie -University of 15 September 26th 2012 15 Birmingham Weight : 10,000 tons Calo.: 5

ALICE Technologies:18 Tracking: 7 Detector: PID: 6 Size : 16 x 26 meters O. Villalobos Baillie -University of 16 September 26th 2012 16 Birmingham Weight : 10,000 tons Calo.: 5

ALICE Technologies:18 Tracking: 7 Detector: PID: 6 Size : 16 x 26 meters O. Villalobos Baillie -University of 17 September 26th 2012 17 Birmingham Weight : 10,000 tons Calo.: 5

ALICE Technologies:18 Tracking: 7 Detector: PID: 6 Size : 16 x 26 meters O. Villalobos Baillie -University of 18 September 26th 2012 18 Birmingham Weight : 10,000 tons Calo.: 5

ALICE ACORDE V0 T0 ZDC FMD PMD Technologies:18 Tracking: 7 Detector: PID: 6 Size : 16 x 26 meters O. Villalobos Baillie -University of 19 September 26th 2012 19 Birmingham Weight : 10,000 tons Calo.: 5

ALICE – dedicated heavy-ion experiment at the LHC TPC ITS TOF TRD HMPID vertexing • particle identification (practically all known techniques) • extremely low-mass tracker ~ 10% of X 0 • excellent vertexing capability • efficient low-momentum tracking – down to ~ 100 MeV/ c 20 13 August 2012 Overview of ALICE K.Safarik

REMINDER Previous Results O. Villalobos Baillie -University of September 26th 2012 21 Birmingham

System Size? • Use boson interferometry (HBT) to estimate system size. = • Measure C q ( ) A q ( ) / B q ( ) – A( q ) is distribution in momentum difference q=p 1 - p 2 for identical bosons – B( q ) is the same, but = − λ + λ + C ( q ) N [(1 ) K q ( ) (1 G ( ))] q measured for track pairs inv = − 2 2 + 2 2 + 2 2 G ( q ) exp( ( R q R q R q that cannot be correlated out out side side long long +2| R | R q q )) (e.g. from different events) ol ol out long September 26th 2012 22 O. Villalobos Baillie -University of Birmingham

System size A. Aamodt et al. Phys. Lett. B696 (2011) 328 Both radii (and therefore volume) and the decoupling time ( τ f ) for the system • (measure of “lifetime”) can be extracted. Shows LHC collisions give rise to an interacting system that is larger (3 × RHIC) and • longer-lived (140% RHIC) than any previously. V ~ 4500 fm 3 , τ ~10 fm/c September 26th 2012 23 O. Villalobos Baillie -University of Birmingham

System size A. Aamodt et al. Phys. Lett. B696 (2011) 328 Both radii (and therefore volume) and the decoupling time ( τ f ) for the system • (measure of “lifetime”) can be extracted. Shows LHC collisions give rise to an interacting system that is larger (3 × RHIC) and • longer-lived (140% RHIC) than any previously. V ~ 4500 fm 3 , τ ~10 fm/c September 26th 2012 24 O. Villalobos Baillie -University of Birmingham

Rapidity Density • The minimum bias rapidity density < d N/ d η > at mid- rapidity rises with √s, both in pp and in PbPb. • pp multiplicity density was not described by Monte Carlo generators without tuning, and initially underpredicted the result. • Production per participant greater by factor 1.9 in PbPb • Monte Carlo generators tuned to pp reproduce PbPb well • Models based on initial-state gluon saturation density have mixed success, depending on specific assumption. (Parton production in a QGP is dominated by gg interactions.) ALICE Collaboration EPJ C(2010) 65 111 EPJ C(2010) 68 89 EPJ C(2010) 68 345 PRL (2010) 105 252301 September 26th 2012 25 O. Villalobos Baillie -University of Birmingham

Rapidity Density dN = ± 1600 75 η d   1 d N ε = m (Bjorken)   T τ   A dy 1 ( ) ετ ≈ × × − 3 1600 0.35 GeV fm π × 2 6 − 3 5 GeV fm ฀ September 26th 2012 26 O. Villalobos Baillie -University of Birmingham

Summary on Bulk Properties • Measurements of global variables of the PbPb system lead to information on the size and energy density of the system. • They indicate that the system created at the LHC has a volume considerably larger than that at RHIC, and lives longer. (R out ≈ R side ≈ 6 fm, R long ≈ 8 fm for low p T ) • The energy density is also larger. The exact size depends on the value given for the “formation time” τ in the Bjorken formula. As the correct value for this parameter is difficult to ascertain, the results are often given for the product ϵ τ . The other parameters in the formula are all unambiguous. September 26th 2012 27 O. Villalobos Baillie -University of Birmingham

Flow Measurements • The system produced in a heavy ion collision is far from static, and is in a process of very rapid expansion. The way in which this takes place is described by “flow”. • Radial flow determines the modifications to the p T spectra coming from the expansion of the system. This gives an additional “boost” to the p T and leads to a hardening of the spectrum. • It is described by a “blast-wave” analysis. September 26th 2012 28 O. Villalobos Baillie -University of Birmingham

Radial Flow β = 0.66 T fo ~110 MeV • Blastwave fit using hydrodynamic model gets expansion velocity and freeze-out temperature. • Comparison with RHIC spectra shows flow effects are stronger at the LHC. September 26th 2012 29 O. Villalobos Baillie -University of Birmingham

Radial Flow RHIC β = 0.66 Blast Wave Fit T fo ~110 MeV • Blastwave fit using hydrodynamic model gets expansion velocity and freeze-out temperature. • Comparison with RHIC spectra shows flow effects are stronger at the LHC. September 26th 2012 30 O. Villalobos Baillie -University of Birmingham