1 / 30

А.Б.Курепин , И.А.Пшеничнов ИЯИ РАН, Москва

Physics at NICA, the view from the Institute for Nuclear Research, Moscow. А.Б.Курепин , И.А.Пшеничнов ИЯИ РАН, Москва. NICA – round table 6 ноября 2008 г. ОИЯИ, Дубна. Outline. Introduction Problem of anomalous charmonium suppression Event-by-Event fluctuations

maeve
Download Presentation

А.Б.Курепин , И.А.Пшеничнов ИЯИ РАН, Москва

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Physics at NICA, the view from the Institute for Nuclear Research, Moscow А.Б.Курепин, И.А.Пшеничнов ИЯИ РАН, Москва NICA – round table 6 ноября 2008 г. ОИЯИ, Дубна

  2. Outline Introduction Problem of anomalous charmonium suppression Event-by-Event fluctuations Ultraperipheral interactions Conclusions

  3. Charmonium • 33 years ago:discovery of J/ψ, 21 years ago: Matsui & Satz • colour screening in deconfined matter →J/ψ suppression • →possible signature of QGP formation • Experimental and theoretical progress since then → situation is much more complicated • cold nuclear matter / initial state effects • “normal” absorption in cold matter • (anti)shadowing • saturation, color glass condensate • suppression via comovers • feed down from cc, y’ • sequential screening (first: cc, y’, J/y only well above Tc) • regeneration via statistical hadronization or charm coalescence • important for “large” charm yield, i.e. RHIC and LHC

  4. Light systems and peripheral Pb-Pb collisions:J/ψ is absorpted by nuclear matter . The scaling variable -L (length of nuclear matter crossed by the J/ψ) •  (J/ψ) ~ exp( -abs L) • Central Pb-Pb collisions:the L scaling is broken - anomalous suppression J/ψ suppression from p-A to Pb-Pb collisions J/ψ production has been extensively studied inp-A, S-UandPb-Pbcollisions by the NA38 and NA50 experiments at the CERN SPS Projectile J/y Target J/y normal nuclear absorption curve NA60 : is anomalous suppression present also in lighter In-In nuclear systems ?Scaling variable- L, Npart, ε ?

  5. Comparison of NA50 and NA60results An “anomalous suppression” is presented already in In-In The normal absorption curve is based on NA50 results. Its uncertainty (~ 8%) at 158 GeV is dominated by the (model dependent) extrapolation from the 400 and 450 GeV p-A data. need p-A measurements at 158 GeV

  6. Suppression by produced hadrons (“comovers”) The model takes into account nuclear absorption and comovers interaction with σco = 0.65 mb (Capella-Ferreiro) EPJ C42(2005) 419 In-In 158 GeV J/y / NColl nuclear absorption comover + nuclear absorption (E. Ferreiro, private communication) Pb-Pb 158 GeV NA60 In-In 158 GeV

  7. QGP + hadrons + regeneration + in-medium effects The model simultaneously takes into account dissociation and regeneration processes in both QGP and hadron gas (Grandchamp, Rapp, Brown EPJ C43 (2005) 91) In-In 158 GeV fixed thermalization time centrality dependent thermalization time BmmsJ/y/sDY Nuclear Absorption Suppression + Regeneration QGP+hadronic suppression Regeneration Number of participants Pb-Pb 158 GeV centrality dependent thermalization time fixed thermalization time NA60 In-In 158 GeV

  8. Suppression due to a percolation phase transition Model based on percolation (Digal-Fortunato-Satz) Eur.Phys.J.C32 (2004) 547. Prediction: sharp onset (due to the disappearance of the cc meson) at Npart ~ 125 for Pb-Pb and ~ 140 for In-In Pb-Pb 158 GeV NA60 In-In 158 GeV The dashed line includes the smearing due to the resolution

  9. J/ψ suppression (SPS and RHIC) J/ψ yield vs Npart, normalized on Ncoll. Unexpected good scaling. Coherent interpretation- problem for theory. Work start - : Karsch, Kharzeev and Satz., PRL637(2006)75

  10. Invariant mass spectra (Au+Au @ 35 AGeV) Identified e+e- After all cuts applied All e+e- Combinatorial bg ρe+e-  e+e-φe+e- π0 γe+e-  π0e+e-ηγe+e- Central Au+Au@35AGeV Simulated statistics: 65k events

  11. Invariant mass spectra J/ψ + ' + combinatorial background superevent 4x1010 central Au+Au@25AGeV UrQMD eventswith target 25mkm J/ψ Ψ’ Invariant mass spectra of tracks identified as electrons by RICH&TRD with reconstructed Pt>1.2GeV/c

  12. beam mult S/B J/ψ eff mass resolution 15 AGeV 2.24x10-6 7 0.12 26 MeV 17 25 AGeV 1.92x10-5 12 0.13 27 MeV 79 35 AGeV 5.95x10-5 12 0.1 27 MeV 83 Dielectron J/Ψ simulation Table corresponds to 4x1010 central collisions : ~ 55 hours of beam time of full CBM interaction range [1 MHz interation rate, 20% centrality] Au beam 10 9 1/sec, target 25 μ

  13. Counting rate ofJ/ψ production

  14. Segmented target Target 250 mkm for J/ΨS/B ~1 Ψ' are not visible Target 25 mkm + for J/Ψ S/B ~12 visible Ψ' - more time to yield statistic Segmented target 5 x 50mkm -7 -3.5 0 3.5 7 cm 300μm beam 2.5°

  15. Invariant mass distribution of background electrons with Pt>1GeV originated in target Target 250mkm Target 5x50mkm Target 1x50mkm

  16. 2. Event-by-event fluctuations Total multiplicity :Ns- number of sources, mi- multiplicity from a single source. Geometry of collision physics! QGP? Second component is not interesting and must be removed Number of interacting nucleons must be known

  17. Beam hole X ZDC geometry. Z Transverse sizes ~1x1 m2; Distance from target - 15 m; Number of modules – 107; Module dimensions – 10x10x1600 cm2

  18. Design and readout Modular Lead/Scintillator sandwich compensating calorimeter. Sampling ratio Pb:Scint=4:1. Expectation:For thickness δPb=16 mm and δScint=4 mm σE/E ~ 50%/√E . Conception Light readout withWLS-fibersfor reliable and uniform light collection. Signal readout with Micropixel APD (MAPD) to avoid nuclear counter effect, detection of a few photons signal, compactness, low cost. Longitudinal segmentation – for permanent calibration of scintillators in radiation hard conditions, rejection of secondary particles. Modular design – transverse uniformity of resolution, good reconstruction of reaction plane, flexible geometry, simplicity.

  19. Measurement of centrality Impact parameter: b~Np, Npis number of interacting (participant) nucleons. Np=A - Nspect=A - Es/EA, Esis sum of spectator energies, measured by Zero Degree Calorimeter (ZDC) ; EAis beam energy. This technique is used in most heavy ion experiments at CERN (WA80, NA49, NA50, ALICE…) and RHIC.

  20. Reconstruction from centers of modules MC simulation Reconstructed angle of reaction plane, deg. Reconstruction of Reaction Plane → →M rk rk – position vector Q = ∑ ----- , of the particle k k=1 → in perpendicular │rk│ to the beam axis plane M – particles in the event used for reconstruction Input UrQMD:reaction plane at 00 Good accuracy is due to fine transverse ZDC granulation. To be improved by taking deposited energy weights.

  21. Z Электромагнитные взаимодействия в столкновениях релятивистских ядер • Ультрапериферические взаимодействия:нет перекрытия ядерных плотностей • Воздействие Лорентц-сжатых кулоновских полей может быть представлено как поглощение эквивалентных фотонов (Weizacker-Williams method) • Фотоядерные реакции: электромагнитная диссоциация и рождение адронов • Реакции фотон-фотон: рождение экзотических частиц Дальнодействующие электромагнитные силы

  22. Спектр эквивалентных фотонов и сечение фотопоглощения: проинтегрировано по b

  23. Модель RELDIS: Relativistic ELectromagnetic DISsociation (ИЯИ,1995-2008,А.Ильинов,И.Пшеничнов ) • Поглощение фотонов ядрами – многостадийный процесс: • поглощение фотона на внутриядерном нуклоне или на квазидейтонной паре (учитывается свыше 100 каналов при энергиях фотонов несколько ГэВ)‏ • внутриядерный каскад образовавшихся адронов • статистический распад возбужденного остаточного ядра – модель SMM: конкуренция испарения нуклонов и кластеров - деление - мультифрагментация

  24. Поглощение одного или двух фотонов приводящее к одиночной диссоциации Разрушается одно из ядер! Следующий к лидирующему 1-2% Лидирующий порядок 98-99% упругий процесс неупругий процесс

  25. Эмиссия нейтронов в электромагнитной диссоциации ядер свинца и золота Фиксированные мишени ~10-30 b Пучки ионов: RHIC& LHC ~100-200 b Для коллайдеров: geff= 2g2beam-1, для LHC – 1.7*107

  26. Schematic view of experimental setup for forward neutron emission measurements for 30 A GeV Pb ions @ CERN SPS S0, S1, SS – plastic scintillator detectors. MBPL and MBPL - Magnets

  27. Energy spectra of the neutron calorimeter in proton and Pb runs 1n ADC spectrum for 30 GeV protons 2n 3n

  28. pure EM part ~ Z2target s/Z2target~ const Phys.Rev. C71(2005)024905 New data:forward neutron emission measurements for 30 A GeV Pb ions @ CERN SPS

  29. Latest data:forward neutron emission measurements for 158 A GeV In ions @ CERN SPS 1n 2n 3n 4n

  30. Conclusions 1. Measurement of charmonium production at MPD NICA is possible 2. For event-by-event physics the development of ZDC is indispensable 3. Electromagnetic interactions at NICA energies will provide new insight to nuclear structure

More Related