1. Swedish teachers program 10/2012 1 ALICE A Large Ion Collider Experiment Outline The quark-gluon plasma :QGP; The ALICE experiment and the particle identification; Data analysis and the scientific method. G De Cataldo, INFN, Bari, It. Thank you very much to Y. Schutz and D. Hatzifotiadou for their help

2. Countries in the ALICE collaboration Swedish teachers program 10/2012 2 G De Cataldo, INFN, Bari, It.

3. The ALICE collaboration Swedish teachers program 10/2012 3 G De Cataldo, INFN, Bari, It.

4. Swedish teachers program 10/2012 4 The physics program of ALICE The club of physicists smashing head-on heavy ions!… The club of physicists smashing head-on heavy ions!… Why ? Trying to de-confine quarks and gluons in a soup (QGP) and stepping backward in the time up to one millionth of second after the Big Bang;Why ? Trying to de-confine quarks and gluons in a soup (QGP) and stepping backward in the time up to one millionth of second after the Big Bang; How ? Heating and compressing nuclear matter (lead- lead nucleus collisions in LHC);How ? Heating and compressing nuclear matter (lead- lead nucleus collisions in LHC); Watching a phenomena thatWatching a phenomena that Lasts in one second as a light in the 15 billions of years after the universe was born, Lasts in one second as a light in the 15 billions of years after the universe was born, Gets a temperature equal to 100.000 times the sun core temperature and Gets a temperature equal to 100.000 times the sun core temperature and Squeeze the matter such that the pyramid of Cheops fits in a needle’s head; Squeeze the matter such that the pyramid of Cheops fits in a needle’s head; The observer is on MARS while describing what is happening on the Earth; The observer is on MARS while describing what is happening on the Earth; G De Cataldo, INFN, Bari, It.

5. Swedish teachers program 10/2012 5 Laboratory 2. The collision energy materialize in quarks and gluons. 1. The accelerated lead nucleus (ordinary matter) undergo head-on collisions. The mini Big Bang : let’s re-do backward the path: 3. The de-confined quarks and gluons experience the Strong Interaction effects: this is the QGP! The soup then moves toward the equilibrium. v/c = 0,99999993 Contraction de Lorentz : 7 fm  0,003 fm t~10 -24 s T~5×10 12 K 4. The plasma dilutes and cools down. 5. Quarks and gluons condensate to form hadrons, and between them the protons: the ordinary matter! t~10 -23 s T~10 12 K G De Cataldo, INFN, Bari, It.

6. ALICE setup ITS TPC TRD TOF PHOS HMPID PMD FMD MUON SPEC. But what does mean ‘to see’ in ALICE end how we do it?? Swedish teachers program 10/2012 6 Tonneau central G De Cataldo, INFN, Bari, It.

7. Lead Collisions 2011 Swedish teachers program 10/2012 G De Cataldo, INFN, Bari, It. 7

8. Products of Pb-Pb collisions @ 2.76TeV for nucleon pairs (Nov. 2010) Products of Pb-Pb collisions @ 2.76TeV for nucleon pairs (Nov. 2010) Swedish teachers program 10/2012 8 G De Cataldo, INFN, Bari, It.

9. Swedish teachers program 10/2012 9 The scientific program About 5.000 particles cross the experiment on each collision; About 5.000 particles cross the experiment on each collision; Carry out the tracking procedure on each particle, identifying them one by one measuring their momenta, electric charge and finally the mass; Carry out the tracking procedure on each particle, identifying them one by one measuring their momenta, electric charge and finally the mass; localize the track origin with about hundred m precision; localize the track origin with about hundred m precision; Identify interesting and rare events in less than 100 s ; Identify interesting and rare events in less than 100 s ; Archive data with a rate of 1,2 Mbytes/s (2 CD/s) which means 1 Pbytes/year (a CD stack of of 4 Km/y) ; Archive data with a rate of 1,2 Mbytes/s (2 CD/s) which means 1 Pbytes/year (a CD stack of of 4 Km/y) ; Give access to the data for the data analysis to about 1000 physicists spread out all over the world. Give access to the data for the data analysis to about 1000 physicists spread out all over the world. G De Cataldo, INFN, Bari, It.

10. The kinetic energy of a proton accelerated from rest by 1V of difference of potential : E k = qV = (½ m p v 2  classic  q=1 (elementary charge; 1.6 x10 -19 C) V=1 Volt E= 1 eV = 1.6x10 -19 Joule A mosquito is approaching you with a speed of 40 km / h. A collision will do nothing. A truck is approaching you with a speed of 40 km / h. A collision will be fatal! (move away!)This is because of the mass of the truck plays an important role. However, a stopped truck, does not scare you. So it is not only the mass, but also the speed, it is the momentum p that makes the difference! The Kinetic Energie E k p = (p x i +p y j +p z k ) = mv (classic) Swedish teachers program 10/2012 10 An oscillating Electric field in LHC (RF) accelerates the protons! Each proton beam @ 7 TeV has the same energy of a 400 t TGV launched ​​ at 150 Km / h! This energy is enough to 'melt 500 kg copper! G De Cataldo, INFN, Bari, It. Physics complements for particle identification Momentum (p)

11. Swedish teachers program 10/2012 G De Cataldo, INFN, Bari, It. 11 What does it means particle identification? Identify a particle it means to measure: its momenta, electric charge and mass. Identify a particle it means to measure: its momenta, electric charge and mass. For what purpose the identification is useful for? In order to study the QGP a good probe is to study the so called ‘strange particles’. For this we have to: In order to study the QGP a good probe is to study the so called ‘strange particles’. For this we have to: 1.First identify the daughter particles in the strange particle decay, 2.and form them look for the ‘strange’ parent particle! ’( see later the exercises).

12. Momentum measurement and electric charge identification Swedish teachers program 10/2012 12 p q R=p/qB p = momentum to be measured R = curvature radius B = magnetic field q = particle electric charge, R G De Cataldo, INFN, Bari, It.

13. HMPID: particle identification by Cherenkov light Swedish teachers program 10/2012 G De Cataldo, INFN, Bari, It. 13

14. TPC, TOF and ITS particle identification Swedish teachers program 10/2012 G De Cataldo, INFN, Bari, It. 14

15. Looking for “starnge” parent particle: the invariant mass for the particle identification Swedish teachers program 10/2012 15 Conservation laws: energy, momenta and electric charge. Then: E=E1+E2 p=p1+p2 Neutre=(+) + (-) This makes me laughing!!! After  ^ -10 s Summary: In order to identify the ‘parent’ particles then the electric charge, the momenta and finally the mass have to be measured on the particles daughter!  + m1p1E1m1p1E1 m2p2E2m2p2E2 Daughter Particles after the decay According to the relativity E = m+p m= E- p 222 222 The invariant mas is then: m = m 1 +m 2 +2(E 1 *E 2 ) -2(p 1* p 2 ) 222 mpEmpE Parent neutral particle before the decay Inter. Beam 2 Beam 1 G De Cataldo, INFN, Bari, It.

16.  The distribution of the invariant mass Swedish teachers program 10/2012 16 m1p1E1m1p1E1 m2p2E2m2p2E2 m For particles ​​ of the same type with random values of momenta, not related to the parent particle, then M=: M = m 1 +m 2 +2(E 1 *E 2 )-2(p 1 p 2 ) 222 G De Cataldo, INFN, Bari, It.

17. The decays to be studied in the excercise: Swedish teachers program 10/2012 17 Lambda pion G De Cataldo, INFN, Bari, It.

18. V0 decay A neutral particle (no tracks left) after its decay produces suddenly two charged traces. In a magnetic field particles of opposite electric charge move in opposite directions.   p + K 0 s      symmetric asymmetric anti Λ→ π + p - Swedish teachers program 10/2012 G De Cataldo, INFN, Bari, It. 18

19. Swedish teachers program 10/2012 19 For the data analysis: after the web, GRID is the CERN answer! Yerevan CERN Saclay Lyon Dubna Capetown, ZA Birmingham Cagliari NIKHEF GSI Catania Bologna Torino Padova IRB Kolkata, India OSU/OSC LBL/NERSC Merida Bari Nantes The huge amount of data per event prevents the analysis to be carried out in ONLY ONE place even with hundred of computers! Then the idea was: Distribute the computation tasks all over the world! How? CPU resources and data storage are spread out all over the world, interconnected via INTERNET and in some a way synchronized. Only with this virtual giant computer the data analysis can be carried out! Great the physicists at CERN! G De Cataldo, INFN, Bari, It.

20. Data analysis for the Physics : Geometry of a Pb-Pb collision Azimuthal Asymmetry Y direction: longer particle trajectory then less particles that get out; Y direction: longer particle trajectory then less particles that get out; X direction: shorter particle trajectory then more particles that get out; X direction: shorter particle trajectory then more particles that get out; Studying this asymmetry we can study the nature of the crossed de-confined matter. Studying this asymmetry we can study the nature of the crossed de-confined matter. 20 Swedish teachers program 10/2012 G De Cataldo, INFN, Bari, It.

21. Data analysis for the Physics : Geometry of a Pb-Pb collision Peripheral Collision Peripheral Collision Large distance between the nucleus center(w.r.t nucleus size), small number of participants then few charged particle produced (small multiplicity). 21 Swedish teachers program 10/2012 G De Cataldo, INFN, Bari, It. Central Collision Central Collision small distance between the nucleus center, high number of participants then many charged particle produced (large multiplicity).

22. And now some Physics 22 As an example : the sum of the signal amplitude in the centrality detector, named V0, (the central the collision the higher the signal) is well represented by means of a simple physics model named Glauber (red line) central periferal Swedish teachers program 10/2012 G De Cataldo, INFN, Bari, It.

23. Theories, models and Scientific Papers Swedish teachers program 10/2012 23 A theory is not true or false but good or bad depending on if it is predictive or not. We consider a theory as a good one until experiments will not provide different results from what predicted! In the spirit of the scientific method (Galileo Galilei 1564-1642), that theory or physics models (less than a theory!) which doesn’t agree with the results is abandoned! Or modified! In the paper below this comparison is discussed. G De Cataldo, INFN, Bari, It.

24. Summary Swedish teachers program 10/2012 24 LHC, smashing lead nucleus at an energy never reached before (5.5 ZTeV) can recreate a state of the matter, named Quark Gluon Plasma @10^ 12 ⁰ C (QGP, a de-confined state of quarks and gluons) that should have existed few microseconds after the Big-Bang! The ALICE experiment has been designed for hunting evidences of the Quark Gluon Plasma state. It combines different techniques of detection that provide unique capabilities of particle identification among the four major experiments at LHC; Thanks to a very powerful computation network, GRID, ALICE can carry out the data analysis and compare the results with the model’s predictions; In the spirit of the experimental method (Galileo Galilei), some models are reinforced, others are abandoned or modified. This is the way humanity improves its knowledge on the fundamental laws of the nature! G De Cataldo, INFN, Bari, It.