А.Б.Курепин , И.А.Пшеничнов ИЯИ РАН, Москва
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
А.Б.Курепин, И.А.Пшеничнов ИЯИ РАН, Москва
Physics at NICA, the view fromthe Institute for Nuclear Research,
Moscow
NICA – round table6 ноября 2008 г.
ОИЯИ, Дубна
Outline
IntroductionIntroduction
Problem of anomalous charmonium Problem of anomalous charmonium
suppressionsuppression
Event-by-Event fluctuations Event-by-Event fluctuations
Ultraperipheral interactionsUltraperipheral interactions
ConclusionsConclusions
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 c, ’– sequential screening (first: c, ’, J/ only well above Tc)– regeneration via statistical hadronization or charm coalescence
● important for “large” charm yield, i.e. RHIC and LHC
J/ψ suppression from p-A to Pb-Pb collisions
Projectile
Target
J/
J/ψ production has been extensively studied in p-A, S-U and Pb-Pb collisions by the NA38 and NA50 experiments at the CERN SPS
J/ normal nuclear
absorption curve
• 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
4.18 0.35mbJabs
NA60 : is anomalous suppression present also in lighter In-In nuclear systems ? Scaling variable- L, Npart, ε ?
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
Comparison of NA50 and NA60 results
An “anomalous suppression” is presented already in In-In
Suppression by produced hadrons (“comovers”)
In-In 158 GeV
The model takes into account nuclear absorption and comovers interaction
with σco = 0.65 mb (Capella-Ferreiro) EPJ C42(2005) 419
J/
NC
oll
nuclear absorption
comover + nuclear absorption
Pb-Pb 158 GeV
(E. Ferreiro, private communication)
NA60 In-In 158 GeV
QGP + hadrons + regeneration + in-medium effects
Pb-Pb 158 GeV
B
J/
/D
Y
Nuclear Absorption
Regeneration
QGP+hadronic suppression
Suppression + Regeneration
In-In 158 GeV
Number of participants
fixed thermalization timecentrality dependent thermalization time
The model simultaneously takes into account dissociation and regeneration processes in
both QGP and hadron gas (Grandchamp, Rapp, Brown EPJ C43 (2005) 91)
centrality dependent thermalization time
fixed thermalization time
NA60 In-In 158 GeV
The dashed line includes the smearing due to the resolution
Suppression due to a percolation phase transition
Prediction: sharp onset (due to the disappearance of the c meson) at Npart ~ 125 for Pb-Pb and
~ 140 for In-In
Model based on percolation (Digal-Fortunato-Satz)
Eur.Phys.J.C32 (2004) 547.
Pb-Pb 158 GeV
NA60 In-In 158 GeV
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
Invariant mass spectra (Au+Au @ 35 AGeV)
ππ0 0 γγee++ee--
ππ00ee++ee--
ηη γγee++ee--
Identified e+e- After all cuts applied
All eAll e++ee--
Combinatorial bgCombinatorial bg
ρρ ee++ee--
ee++ee--
φφ ee++ee--
Central Au+Au@35AGeV
Simulated statistics: 65k events
Invariant mass spectra Invariant mass spectra J/ψ + J/ψ + ' + ' + combinatorial background combinatorial background superevent 4x10superevent 4x1010 10
central Au+Au@25AGeV UrQMD eventscentral Au+Au@25AGeV UrQMD events with target with target 25mkm25mkm
J/J/ψψ
Ψ’Ψ’
Invariant mass spectra of tracks identified as Invariant mass spectra of tracks identified as
electrons by RICH&TRD with reconstructed electrons by RICH&TRD with reconstructed
Pt>1.2GeV/cPt>1.2GeV/c
Dielectron J/Dielectron J/ΨΨ simulation simulation
27 MeV27 MeV
27 MeV27 MeV
26 MeV26 MeV
mass mass resolutioresolutio
nn
5.95x105.95x10-5-5
1.92x101.92x10-5-5
2.24x102.24x10-6-6
multmult
79790.130.13 121225 AGeV25 AGeV
8383 0.10.1121235 AGeV35 AGeV
1717 0.120.12 7715 AGeV15 AGeV
J/J/ψψ eff effS/BS/Bbeambeam
Table corresponds to 4x10Table corresponds to 4x101010 central collisions central collisions : ~ 55 hours of beam time of full CBM : ~ 55 hours of beam time of full CBM interaction range [1 MHz interation rate, 20% interaction range [1 MHz interation rate, 20% centrality] centrality]
Au beam 10Au beam 10 9 9 1/sec, target 25 1/sec, target 25 μμ
BS
S
35 AGeV
CBM L=1029 640 1/hour
√ s = 8AGeV
MPD L=1027 30 1/hour
Counting rate of J/ψ production
Segmented targetSegmented target
Target 25 mkm Target 25 mkm
++for J/for J/ΨΨ S/B ~12 S/B ~12
visible visible ΨΨ ''
--more time to yield more time to yield
statisticstatistic
Target 250 mkm Target 250 mkm
for J/for J/ΨΨ S/B ~1 S/B ~1
ΨΨ' are not visible' are not visible
beam
2.5°
-7 -3.5 0 3.5 7 cm-7 -3.5 0 3.5 7 cm300μm
Invariant mass distribution of Invariant mass distribution of background electrons with Pt>1GeV background electrons with Pt>1GeV
originated in targetoriginated in target
Target 250mkmTarget 250mkm
Target 1x50mkmTarget 1x50mkm
Target 5x50mkmTarget 5x50mkm
2. Event-by-event fluctuations
Total multiplicity : Ns- number of sources,
mi- multiplicity from a single source.
i
Ns
i
mN
1
s
NmN
Nm
mNs
222
mNN sGeometry of
collision
Second component is not interesting and must
be removed
physics! QGP?
Number of interacting nucleons must be known
ZDC geometry.
Beam hole
X
Z
Transverse sizes ~1x1 m2;
Distance from target - 15 m;
Number of modules – 107;
Module dimensions – 10x10x1600 cm2
Design and readout
ConceptionLight readout with WLS-fibers for 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.
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 .
Measurement of centrality Impact parameter: b~Np ,
Np is number of interacting (participant) nucleons.
Np=A - Nspect=A - Es/EA ,
Es is sum of spectator energies, measured by Zero
Degree Calorimeter (ZDC) ;
EA is beam energy.
This technique is used in most heavy ion experiments at CERN (WA80, NA49, NA50, ALICE…) and RHIC.
Reconstruction of Reaction Plane
Input UrQMD: reaction plane at 00
MC simulation
Reconstruction from centers of modules
Reconstructed angle of reaction plane, deg.
Good accuracy is due to fine transverse ZDC granulation. To be improved by taking deposited energy weights.
→ → 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
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
Z
Дальнодействующиеэлектромагнитные силы
Спектр эквивалентных фотонов и сечение фотопоглощения: проинтегрировано по b
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
Поглощение одного или двух фотонов приводящее к одиночной диссоциации
Следующий к лидирующему 1-2%Лидирующий порядок 98-99%
упругий процесс
неупругий процесс
Разрушается одно из ядер!
Эмиссия нейтронов в электромагнитной диссоциации ядер свинца и золота
Фиксированные мишени ~10-30 b
Пучки ионов: RHIC& LHC ~100-200 b
Для коллайдеров:eff
= 22beam
-1, для LHC – 1.7*107
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
Energy spectra of the neutron calorimeter in proton and Pb runs
ADC spectrum for 30 GeV protons
1n
2n
3n
New data:forward neutron emission measurements for
30 A GeV Pb ions @ CERN SPS
pure EM part ~ Z2target
/Z2target
~ const
Phys.Rev.C71(2005)024905
Latest data:forward neutron emission measurements for
158 A GeV In ions @ CERN SPS
1n
2n
3n 4n
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