1. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 1 Hideto En’yo Kyoto University Nuclear Matter Probed with  Meson - exploring the lost symmetry- Hideto En’yo Kyoto University Syllabus Syllabus  Introduction  What is MASS ?  How to measure particle mass in nuclear matter  Related Experiments  KEK-PS E325 experiment  Physics  Spectrometer  Results  Summary  Summary  Entertainment

2. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 2 Mass in QCD Particle Data Booklet –m u = 1.5~5 MeV m  = 140 MeV –m d = 3~9 MeV m  = 770 MeV –m s = 60~170 MeV m   = 1020 MeV When Particle M decays M 2 =  e i 2  p i 2 invariant mass What happens in Media ? In Free Space E 2 =M 2 +P 2 Mass is effectively given, but the state is GROUND LEVEL Can we restore the symmetry ? How we measure ?

3. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 3 What Theorists Say ? quark condensate : order parameter to indicate how much the symmetry broken but not an observable → Mass of Vector Meson,  M v = 2 x M q eff + small interaction term

4. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 4 Bound Nucleons Imagine that a neutron ( or proton ) in Oxygen nuclei made GUT decay in Kamiokande. (assume that you have a perfect detector ) n → π + + e  M n 2 →  E π + E e ) 2  P π + P e ) 2 M n = 939.6 MeV, M n = 938.3MeV ????? More precisely 16 O → π + + e  + 15 O * (M n +M 15O ) 2 →  15O + E π + E e ) 2  P 15o + P π + P e ) 2 You measure 16 O levels

5. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 5 Moving Mesons in Media In-media meson modification –Observed Mass is not Lorentz Invariant shift of resonance position resonance broadening/narrowing → DISPERSION be small

6. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 6 How to Measure Mass in Media  1: Search for a deeply bound meson state, Measure the level. (possible only at normal nucler density)  2: Invariant Mass Spectroscopy, determine the dispersion of mesons in nuclear media ( even in hot or dense mater)  3: Compare Decay Branching Ratios to different channels (decay Q value must be sensitive) Meson spectroscopy ( in free space) can be considered as the mass spectroscopy for the valence quarks in normal vacuum, with which it is difficult to answer “what is the origin of the mass”.

7. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 7 Hurdles Many Unknown ( theories exist but almost no experiments ) –Temperature & dependence of –Temperature & time evolution →CERN/RHIC/LHC –Density & dependence of –Density & time evolution →BNL/JHF –Dispersion & Broadening A lot of inputs from experiments needed, even at the normal nuclear matter density.

8. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 8 Present and Future Experiments CLUES Experiment Measurements Interests CERES/HELIOS-3  modification Temp. dep. KEK-TANASHI ES  modification Density dep. GSI  modification Density dep. The efforts to be continued at RHIC and LHC (temperature dependence) Present & future experiments to measure the mass of vector mesons at normal nuclear matter density. KEK-ES:  +A →  +A*(  →  +  ) (Published) KEK-PS: p+A→  +X(  → K+K  /e+e  ) (Running) SPring-8:  + →  +A*(  → K+K  ) (Ready to run ) GSI: d +A→3He+A*(  bound states) (Ready to run ) GSI-HADES:  +A→  +A* (  →e+e  ) (Preparation, 2001?)

9. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 9 KEK-PS E325 to measure  decays in nuclear matter  is narrow resonance (  =4.4MeV)  Q=38MeV –  = 4.4MeV sensitive to resonance-shape change –  Q= 38MeV sensitive to the decay branching ratios )  →K + K  (49%)  →e+e  (3x10 -4 ) KK Thres hold in Free Space K modification ?  modification ?

10. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 10 E325 PHYSICS E325 PHYSICS Expected Signal (electron pairs) KEK-PS E325 to measure KEK-PS E325 to measure  decays inside a nucleus –In 12GeV p+A (C/CH_2/Cu/Pb)→  + X –Observables –Invariant mass spectrum;  →K + K  and  →e+e  –Branching ratio; Br(  →K + K  )/Br(  →e+e  –Less ambiguous data on the  modification –Also Sensitive to the production and interaction of  in nucleus

11. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 11 Particle Production follows A   for –Drell-Yan lepton pairs –J/  –perturbative production  for  -fragmentations  production ? Br(  →K+K  ) / Br(  →e+e  Pb Br(  →K+K  ) / Br(  →e+e  C to be free from production mechanism Mechanism of  Production at 12 GeV J/    Drell-Yan 2/3 XFXF 300GeV p+A →  120GeV p+A→  →KK

12. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 12 Some Tips of E325 Expected mass shift is 20~40 MeV ( Hatsuda- Lee). Focus on slowly moving  's, p =~1GeV/c(lab). About 10% of  's will decay inside a nucleus if nothing happens. Secondary peak may enhance when low  's are selected. The ratio (  →K+K  )/(  →e+e  ) is sensitive to in-media modification of phi and/or K natural width of  is narrow (4.4MeV), but some broadening can happen.. Estimations are:  =   N    0  <20MeV   {  N} < $10mb, total cross section (from  +A→  )    =0.7,  0 =0.16/fm3   →  + *K  *(K  N→  X)  Klingle and Weise  ~44MeV (at rest) 10 9 /sec primary protons on thin (0.1%) nuclear target to suppress  conversions.

13. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 13 Brief Mile Stones and Status 1994 March KEK-PS PAC conditionally approved 1995 March KEK-PS PAC approved 1996 July- Construction started 1996 November Engineering Run 1997 June, First Physics Run with K+K . 17days –Data accumulation mainly with K+K  channel trigger –Beam Intensity 1~2 x10 8 $ protons/spill –0.6% interaction target (10 6 interaction/spill) –C/CH2/Pb 3 targets in-line –165GByte Data (160M events) collected in 50 shifts 1998 March, Completion of Spectrometer, 1998 April -May: Production Running of 29 days –Parallel Trigger. K+K-/ e+e- –Beam Intensity 1~2 x 10 9 protons/spill –0.1% interaction target (10 6 $ interaction/spill) –$C/CH2/Cu 3 targets inline –502GByte Data (180M events) collected in 85 shifts 1999 June 60 shifts Data Taking performed –Parallel Trigger. K+K-/ e+e- –Beam Intensity 1~2 x 10 9 protons/spill –0.2% interaction target (10 6 $ interaction/spill) –360GByte Data (180M events) collected in 85 shifts 2000 May 80-100 shifts Data Taking Expected

14. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 14 E325 collaboration Kyoto University –H.Enyo, H.Funahashi, T.Haseyama, M.Ishino, H.Kanda, M.Kitaguchi, S.Mihara, M.Miyabe, T.Miyashita, K.Miyazaki, T.Murakami, R.Muto, M.Naruki, K.Ozawa, H.D. Sato, T.Tabaru, S.Yamada, S.Yokkaichi, Y.Yoshimura T.I.T. – K.Hamada, Y.Sakemi, T.A.Shibata CNS, University of Tokyo –H.Hamagaki KEK –J.Chiba, M.Ieiri, O.Sasaki, M.Sekimoto, K.Tanaka RCNP –M.Nomachi \ 250,000,000/5students/5years=\10,000,000

15. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 15 E325 SETUP

16. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 16 Trigger Counters TOF AC GCs Lead Glass Calorimeter Karm Accceptance Inside Magnet AC vetos 99% of pion (P>0.55GeV/c) TOF  t~200psec 2-Stage e-ID reject 99.9% pions

17. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 17 Typical Event

18. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 18 Spectrometer Performance  →p   Invariant Mass Spectrum  M  = 1115.1MeV/c 2 (PDG 1115.7MeV/c 2)   M  = 2.2MeV/c 2  →  M  = 1.2MeV/c 2

19. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 19  →K + K  Invariant Mass Spectrum 0.4<M kk <0.6 GeV/c2, P k <1.2GeV/c Two kaons are in the same arm. Mixed event background is over-plotted (shaded area). ALL CH 2 C Pb

20. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 20 Target Dependence of Width Resonance positions & widths are consistent with those in free space (within the statistic of ‘97 data ) Pb data looks wider though.

21. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 21 Target Mass Dependence of   →K + K    =0.98  0.10  Absolute cross section is not well determined yet.  is surprisingly large

22. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 22  Comparison to other data consistent with the high energy date (Einc > 100GeV) where the  is produced somewhat perturbatively. Surprising that similar production mechanism even at 12GeV May suggest the perturbative production of  even at 12 GeV

23. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 23 ‘ 99 data We now have enough data to identify decays outside and inside nuclei. Very Preliminary

24. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 24 Summary and Outlook Study of in-media modification of meson is very important and interesting to understand the broken chiral symmetry in QCD. The experiment, E325, at KEK 12GeV PS measures 12GeV p + A →  + X reactions in both  →K + K  and  →e+e  channels. To observe possible changes of the ratio, Br(  →K+K  )/Br(  →e+e  ), and of the shape of the invariant mass peak under the normal nuclear density (  and T = 0). Especially we put an emphasis on the detection of slowly moving  mesons ~ 1-2GeV/c in lab., subject to thus decay in Nuclear Media. The ‘97  →K+K  data have been analyzed so far (1/5 of the data already collected, 1/10 of data to be acquired). The results shows –No statistical significance on the mass shape deformation (YET) –Strong A dependence (  =0.97  0.10 ) in the production No significant increase of  with p T The ‘99  →K+K  data are still preliminary, with some hint of in-media decay component in the mass shape. Many new experimental results including this experiment will be available soon, from GSI, Spring-8, and KEK.

25. １１ -JAN-2000 @ RIKEN Winter School Hideto En'yo, Kyoto University 25 Entertainment General Physics Questions Think when you are on the lift  Q1: You are freely in free space (without gravity). Can you turn right around ? (you can’t blow )  Q2: You have 1 litter of hot red water (100 o C) and 1 litter of cold blue water (0 o C). You want to warm up the blue water with the red water. How high you can warm it up ? (do not use extra energy from outside)