1. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Susumu SATO Contents 1) Introduction ~ Relativistic heavy ion collision ~ 2) Thesis motivation ~  measurement ~ 3) Experimental setup ~ WA98 at CERN-SPS ~ 4) Data analysis ~ corrections and errors ~ 5) Experimental Results ~ ,  p spectra &  yield ~ 6) Discussion ~ low m t enhancement of inclusive  spectrum ~ Summary Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS

2. CERN-SPS-WA98 Susumu SATO Picture of Relativistic Heavy Ion collisions To understand fireball, need picture during “cooling with expansion” [1: Before collision (   ~17 at SPS)] - Lorentz contracted [2: During collision (  ~1fm/c)] →stopping/heating →hot/dense fireball [3: After collision] →(thermal/chemical equilibrium) →”cooling with expansion” →thermal/chemical freeze out → hadrons( ,K,p,…), e,  …detection Fireball

3. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO m t – m (GeV) mt-scaling in proton – proton collisions Single Particle Spectra (pp collisions) Nucl.Phys.B100(75)237 (1)Similar shape, and (2)Similar slope for different particle species (called m t -scaling)

4. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO m t – m (GeV) Single Particle Spectra (nucleus - nucleus collisions) Nucl.Phys.A610(96)175c (1)Different shape, and (2)Different slope for different particle species Different shape and slope are observed.

5. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Two particle HBT correlation Source size as a function of relative momentum quantum interference to measure source size (R) R C 2 : detection probability of two particles at the momentum of p 1 and p 2 (R=6fm, =1)

6. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Two particle HBT correlation in nucleus nucleus collisions Source size as a function also of average momentum Beam Direction (z) Transverse Direction (x,y) q Eur.Phys.J. C2(98)661

7. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Expanding Fireball Model (1) mass dependence of m t spectra slope p －－ p－p－ ++ K+K+ K － Naively, Expansion Fireball is applicable ! NPA610(96)175 →linear mass dependence ↓ parameterized naively T = T f +mass ・ 〈  f 〉 2 Mass(GeV/c 2 ) Slope(GeV)

8. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Expanding Fireball Model (2) ~ example of good parameterization ~ Good explanation both for singles and two particle correlation, but not using lower m t -region (1)Single spectra: transverse kinetic energy (m t ) spectra PRL80(98)3467 →parameterization for different particle species T f ~139MeV, 〈  f 〉 ~0.42c (2) Two particle HBT correlation Habilitation(’97/T.Peitzmann) →Boost invariance for expansion 〈  f 〉 =  R/  f ~ 0.43  0.16c

9. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Thesis Motivations (1) Measurement of particle production of a new particle species;  →  (1232) in 158 A GeV Pb + Pb central collisions. (2) As a basic problem to understand both single particle spectra and HBT correlation, low mt pion enhancement is observed. →By using the result of explicit measurement of  resonance, the contribution of  to low m t enhancement is acquired, then aiming to get footing of the validity of the expanding fireball model.

10. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Authors Contributions Design of experimental detector ● Time-of-Flight (TOF) detector ● Optimal alignment of chambers in magnetic spectrometer Construction, test, installation, and operation of detectors ● TOF detector ● Streamer tube tracking (STD) detector ● Start counter Programming of control and reconstruction software ● HV control for TOF ● Online monitoring for TOF, STD ● Momentum reconstruction Physics Analysis ● Pion and proton single spectrum ● Yield of  (1232) resonance

11. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Δ ++ resonance ● Lowest resonance of nucleon ● M ~ 1232MeV (in Breit-Wigner function ） ● c  ~ 1.8 fm; (  ~111MeV) ● Isospin3/2, Spin 3/2 ● Decay into pion and proton with >99% branching ratio ● Decayed pion gives lower transverse kinetic energy y Pt (m t ) (GeV/c) 0 1 0 0.4 0.8  ++ p ++

12. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO PAD Cham. Beam ( 208 Pb:158AGeV ) Magnet Start TOF (Stop counter) Streamer Tube Det. LEDA(EM.Cal.) +P.ball, SPMD PMD ZDC(Had.Cal.) MIRAC(Had.Cal.) 21.5m Target ( 208 Pb: 0.239mg/cm 2 ) Characterize Fireball from various aspects [Hadron] momentum + PID; w/Mag. Spectr. [Photon] E  w/EM.Cal. [Hadron] global E T, E 0 ; w/Had.Cal. [Photon] mult. distr.; w/PMD [Charged particle] mult. distr.; w/SPMD, P.ball WA98 experimental setup

13. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Magnetic spectrometer is in good operation ～ 1% at 2GeV/c 0 1 2 3 4 5 0 1% σ p / p 2% 0.5 % 1.5 % -0.4 0 0.4 10k 5k N start  ~30ps Detector resolutions (p, T start, T tof ) p(GeV/c) T dif (ns) T tof (ns) N 800 400 0 0.8 -0.8  ~85ps tof   ~1.3mm,  // ~2.1mm (PAD 1 )   ~2.6mm,  // ~7.0mm(STD 1 )

14. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO 0 Clear Particle Identification by ToF method ~0.02 (GeV/c 2 ) 2 at 2GeV/c for π 0.00 0.10 02 0.05 413 m 2 (GeV 2 /c 4 ) p(GeV/c) 2 4 6 8 00.511.5 p(GeV/c)  p K＋K＋ Particle Identification σ m 2 (GeV/c 2 ) 2

15. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Parameterization [1] for  , p single particle spectra Kinematical parameters Transverse kinetic energy (longitudinal) rapidity : Lorentz invariant Lorentz invariant differential yield if  symmetry

16. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Measure around mid-rapidity, where hot fireball is expected the most. (←y target =0) y cm =2.9 ( y beam =5.8 →) Geometrical Acceptance Fireball mt-m(GeV)

17. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Data selection Event selection Single beam (3  in ADC start ) FEE linear region (5.7% in T dynamic ) not after-chamber-spark (0.8sec) event ADC start 1 [ch] ADC start 2 [ch] Track selection image on target (3  in B // direction) image on TOF2 (2.5  on 2-D plane) PID selection m 2 (2.5  in the p)

18. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Geometrical acceptance and Efficiency correction Averaged eff.   PAD1 83%   PAD2 80%   STD1 91%   STD2 97%  p PAD1 STD2STD1 PAD2 By the Monte Carlo Simulation (GEANT3.15) cc X mtmt gg y Y

19. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Single spectra Slope (MeV) WA 98 NA 44 (*) π+π+ 142 ±3 156 ±3 p 251 ±25 289 ±7 mark in plot filled open (*) Nucl.Phys.610(96)175 m t -m(GeV) Consistent shapes with other experiments

20. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Parameterization [2] for  yield by invariant mass method Invariant mass Invariant mass distribution should be evaluated Invariant mass (GeV)

21. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Mixed Event technique Combinatorial background is assumed to be proportional to mixed events Mixed events: p and  + from different events paired in 100 every events EVENT 1 p   EVENT 2 p   example Invariant mass (GeV)

22. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Two normalization methods Two methods should be consistent q:relative momentum of the pair in its C.M. frame,  :180MeV/c (1)Tail method normalize only in higher m inv region (2) Breit-Wigner + Background method normalize in any m inv region, assuming Yield  ++ follows Relativistic Breit-Wigner (PRL79(’97)4354) Invariant Mass (GeV)

23. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Clear yield can be extracted by tail method Tail method  =0.086  0.014 (GeV) E 0 =1.237  0.006 Invariant mass (GeV)

24. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Breit-Wigner + Background method Again, clear yield can be extracted by B.W.+BG. method Invariant mass (GeV)

25. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO (3)Local multiplicity (N  ) on TOF Systematic error of N  / ev. on extraction method Less dependence on extraction parameters (2) Tail method: 0.021 (1)Breit-Wigner + B.G. method: 0.022 N  / ev. M th. (GeV) 1.4 1.5 1.6 1.7 1.4 1.5 0 0.05 0.10 0.022 0.018 N  =2N  =3N  =4 Nev. Poisson =2.6 0 1k 2k NN 246 0

26. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO For, Statistical Error Major contribution of error is large Combinatorial Back Ground Error propagation gives ( 50.0% ) ( 49.9% ) ( < 0.1% )

27. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Isospin consideration Factor from N p /N  ++ to N nucleon /N  is 2.0.

28. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Yield summary table At SPS, delta yield is, for the first time, directly measured Value and Statistical Error  ++ / spectrometer /ev. (raw) 0.022  0.010 proton / spectrometer/ev. (raw)1.080  0.010  ++ /proton (raw) 0.021  0.009  trk (3or4cham.) 0.79  0.02  PID 0.60  0.02  geo 0.145  0.005  ++ /proton (  trk,  PID,  geo corrected) 0.31  0.14  /nucleon (isospin corrected) 0.62  0.28 (stat.) (45%) Systematic Error Uncertainty of Tracking efficiency  0.06 (sys.) (10%) Difference in normalization method  0.02 (sys.) ( 4%) Difference for different local multiplicity  0.08 (sys.) (13%)

29. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Higher population is seen at SPS PLB477 (2000) 37-44 Δ(1232) nucleon (%) 100 80 60 40 20 0 110100 E beam (AGeV) Population ratio: Δ/ nucleon Acquired from  / p, Isospin correction done for

30. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Low m t enhancement is seen in local m t slope (Next) m t – m (GeV) 00.40.60.2 10 2 10 ++ Neighboring several points for local m t slope 1 Low m t enhancement in Pb + Pb (1) 10 3 0.81

31. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO The m t enhancement is seen in  + spectrum in Pb + Pb collisions Center of fitting region in m t – m (GeV) Local slope (GeV) Low m t enhancement in Pb + Pb (2)

32. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO pp collision is described well in m t exponential m t – m (GeV) pp collisions 100 10 1 00.40.60.2 Fitting Line y=a  exp(-x/b) a=82.5±3.7 b=0.153±0.003  2 /n.d.f=8.8/6 Nucl.Phys.B100(’75)237 ++ at mid-rapidity

33. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Candidates of low mt enhancement There are more than one candidates (1) Collective motion (2) Coulomb effect (3) Resonance decay  ++  ++ e.g. Collective radial expansion Repulsion/Attraction from Charges ++  decay gives lower m t  by kinematics y Pt (m t ) (GeV/c) 0 1 0 0.4 0.8  ++ p ++ p

34. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Collective motion (Thermal+expansion)  spectra shape is little affected by Collective motion  MeV 〈  〉 =0.42c Describing well for different particle species except low m t , and shape of  is little affected by collective motion PRL80(’98)3467 consistent also with two particle HBT correlation Dashed line: exponential for eye guide m t – m (GeV)

35. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO 00.40.2 0 1.0 2.0 w/Coulomb No Coulomb Low m t Enhance Low m t enhancement is seen in both charge, and Coulomb effect appears as difference between  + and  –. Coulomb effect Coulomb m t – m (GeV)

36. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Contribution of Δ Resonance “thermal source” + “Δ resonance decay” is consistent with the low-m t enhancement of π ＋. Δ( invariant mass) with a factor (1+α) →consistent with simulation thermal model T=139 MeV, 〈  〉 =0.42c +  included evaluation m t – m (GeV) (a.u.)

37. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO Conclusion (1)For the systematic study of hadron production in 158 A GeV Pb + Pb collision, magnetic spectrometer with good PID capability is constructed. (2)At 158 A GeV Pb + Pb collisions,  + and p inclusive single m t spectra are measured. Inverse slopes are 142  3 MeV (fitting region: mt – m > 0.2 GeV) for  + and 251  25 MeV for proton. In the pion spectrum, clear low m t enhancement is observed. (3) 158 AGeV Pb + Pb collisions,  resonance yield is, for the first time, measured directly. The  /nucleon ratio is 0.62  0.28 (stat.)  0.16 (sys.). (4) Spectrum shape with consideration of  decay on thermal expanding fireball follows low-m t enhancement of π ＋. The additional factor is consistent with a cascade simulation that gives contribution of  decay with re-scattered proton.

38. Study of  ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS CERN-SPS-WA98 Susumu SATO At SPS,  is not measured, while AGS tells its importance At AGS, good description with  decay in RQMD PLB351(95)93  at AGS (not directly measured) and Measured PID at SPS