1. Status and plans of the ion program of NA61 at the CERN SPS
Katarzyna Grebieszkow Warsaw University of Technology for the NA61/SHINE Collaboration
Status and plans of the ion program of NA61 at the CERN SPS
K. Grebieszkow for the NA61 Collaboration
"Status and plans of the ion program of NA61 at the CERN SPS"
The NA61/SHINE experiment at the CERN SPS is a new program to study hadron
production in hadron+hadron, hadron+nucleus and nucleus+nucleus interactions.
The main goal of the NA61 ion program is to explore the most
interesting region of the phase diagram of strongly interacting matter.
Within the expected (T - mu_B) interval we plan to study the
properties of the onset of deconfinement and to search for the signatures
of the critical point. Such a 2D scan of the phase diagram will be performed by
varying the energy (13A-158A GeV) and system size (p+p, Be+Be, Ar+Ca, Xe+La)
of the collision. The first data samples of the p+p energy scan were recorded
in 2009 and 2011.
This presentation will summarize the status and plans of the NA61/SHINE
ion program. In particular the detector upgrades, data taking schedule and
the first results on spectra and correlations will be discussed.
Critical Point and Onset of Deconfinement (CPOD) November 7-11, 2011, Wuhan, China

2. The most interesting region of the phase diagram is covered by SPS!
1. Evidence for onset of deconfinement (kink, horn, step) is observed by NA49 at EOD30A GeV (Alt et al., PR C77, (2008))
2. Critical point of strongly interacting matter may be located at SPS energies
(TCP, BCP ) = (1622, 36040) MeV
(Fodor and Katz, JHEP 0404, 050 (2004))
BCP = 360 MeV  ECP  50A GeV
(Beccatini, Manninen, Gaździcki, PR C73, (2006))
(TCP/Tc, BCP /TCP) = (0.95, 1.10.2)
Tc – cross-over temperature at B = 0
Gavai, Gupta, PR D71, (2005)
(TCP, BCP) = (0.927(5)Tc, 2.60(8)Tc) =
(~157, ~441) MeV
Li et al. RIKEN-BNL Workshop, Oct. 4, 2011
Open symbols: early stages
Full symbols: chemical freeze-out points
CP should be searched above the
energy of the onset of deconfinement
ECP > EOD  30A GeV (NA49 data)

3. NA61/SHINE at the CERN SPS
Fixed target experiment in the north area of the CERN SPS
Based on the upgraded NA49 detector
Started in 2007
Beams:
ions (Be, Ar, Xe) at 13A - 158A GeV
hadrons (p, p) at GeV
Based on:
Report from the NA61/SHINE experiment at the CERN SPS
CERN-SPSC ; SPSC-SR-091
Status of the evidence for the onset of deconfinement and
the urgent need for primary Ar beams
photo:
CERN-SPSC ; SPSC-M-775
The 2010 test of secondary light ion beams
CERN-SPSC ; SPSC-SR-077
Measurements of the Cross Sections and Charged Pion Spectra
In Proton-Carbon Interactions at 31 GeV/c
Phys. Rev. C84 (2011)

4. NA61/SHINE physics program
Hadron production in p+p, p+A, h+A, A+A at various energies
Search for the critical point of strongly interacting matter
Study of the properties of the onset of deconfinement
Study high pT particles (energy dependence of nuclear modif. factor)
Motivation: suppression of high pT particles at RHIC and LHC energies (manifestation of parton energy loss in a dense medium)
Hypothesis: for lower energy collisions, where deconfined matter is not formed, such suppression should disappear
Obtain precision data on hadron production (spectra)
reference measurements of p+C interactions for the T2K experiment for computing neutrino fluxes from the T2K beam targets
reference measurements of p+C, p+p, p+p, and p+C interactions for cosmic-ray physics (Pierre-Auger and KASCADE experiments) for improving air shower simulations
Pion spectra in p+C interactions at 31 GeV are published (PR C84, (2011)). They are already used to improve beam neutrino flux predictions and to adjust models (UrQMD , Fritiof ) used in neutrino and cosmic-ray experiments

5. Data sets planned to be recorded by NA61 within the ion program and those recorded by NA49

6. Comprehensive scan in the whole SPS energy range (13A-158A GeV) with
light and intermediate mass nuclei
First time in history when such a 2D scan (energy, system size) will be performed
Estimated (NA49) and expected (NA61) chemical freeze-out points according to
Beccatini, Manninen, Gaździcki, PRC73, (2006)

7. ? NA61 plans: onset of deconfinement
Search for the onset of the horn in collisions of light nuclei ?
Expectation for energy and system size scan: similar structures (kink, horn, step); vanishing for small systems In particular the ''horn'' like structure is expected to be similar for Ar+Ca and Pb+Pb collisions and then rapidly disappear for smaller systems

8. NA61 plans: search for the critical point
Search for the hill of fluctuations CP
signal
w, pT, ...
Be+ Be T 13 B
Increase of critical point signal (multiplicity and average pT fluctuations, intermittency, etc.) for system freezing-out near the critical point Non-monotonic dependence of critical point signal on control parameters (energy, centrality, ion size) can help to locate the critical point
Already observed in NA49: fluctuations of average pT, multiplicity, multiplicity of p+p- pairs, net-proton density tend to a maximum in Si+Si (Si+A) collisions at 158A GeV
→ strong motivation for future experiments

9. Main upgrades:
2007: Construction of the forward ToF wall to identify particles with p < 3 GeV/c and  < 400 mrad
(extended ToF acceptance to p  1 GeV/c)
2008: Replacement of the TPC digital read-out and DAQ (increase of the event rate by a factor of  10; important i.e. for high pT particles)
2011: Replacement of Forward Calorimeter (VETO) by Projectile Spectator Detector with resolution
s(E)/E  0.55/√(E/(1GeV))
5 x better than in NA49
Resolution of 1 nucleon !
Important for fluctuation analysis
2011: Installing helium beam pipes
Ready for 2011 Be run: Z-detectors (measure ion charge for on-line selection of secondary ions, A-detector (measures mass composition of secondary ion beam)
Low Momentum Particle Detector (LMPD), for centrality determination in p+A, is ready and the pilot p+Pb data were registered in 2011
SHINE (fixed target) experiment at CERN SPS Successor of the NA49 experiment
SHINE – SPS Heavy Ion and
Neutrino Experiment
LMPD
data taking since 2007

10. Secondary ion beam production in NA61Pb
primary Pb beam
from the SPS
fragmentation
target
Pb beam fragments
Fragment
separator
Fragment separator will be used by NA61 to produce clean light-ion beams (for example Be)
Tested of 13.9A and 80A GeV
secondary ion beam

11. Secondary Ion Beam Line for NA61
Double magnetic spectrometer to separate ion fragments corresponding to selected magnetic rigidity Br
Fragmentation target (T2) length optimized to the desired fragment production
Degrader (Cu plate where ions lose energy dE/dx ~ Z2) allow to reach required beam purity
Tested in 2010 for 13.9A and 80A GeV Pb ion beams
momentum
selection
momentum
selection

12. secondary ion Z-spectrum
Results of the 2010 test run
(test of secondary light ion beams)
secondary ion Z-spectrum
without degrader He
During the test:
fragment separator scheme was successfully used to produce light ion beams so far with highest momentum 80A GeV/c
for the first time primary Pb beam of momentum as low as 13.9A GeV/c was accelerated in the SPS and extracted onto the T2 target in the North Area
The test results indicate that:
the properties of the secondary beam are sufficient to reach the basic physics goals of NA61
7Be beam is preferred for the energy scan with light ions (2011/2012)
Pb beam at 13.9A GeV Be Li C B O N
Be beam selected
with degrader Be
it is possible to obtain clean Be beam
Primary Pb beam at 13.9A GeV/c corresponds to 12.75A GeV/c secondary light (A»10) ion beam (difference is caused by energy loses in fragmentation target and degrader)

13. He beam pipes ↗
Channeling of high intensity heavy ion beam through the gas volume of the Vertex TPCs has limitations when compared to proton beam
Delta electrons produced in the gas volume inside VTPCs from heavy ion beam-gas interactions (electrons kicked off from TPC gas atoms by beam ions/spectators) may significantly increase the background in TPCs and distort measurements of event-by-event fluctuations
Example of the effect from a single d-electron in VTPC-1(spiralling low-energy knock-on electron)
Registered in 2009
VTPC-1
VTPC-2
Installation of the helium beam pipes in the VTPC gas cage (around the beam line) - a reduction of the delta-electron background by a factor of 10

14. Helium-filled beam pipes were successfully mounted inside fragile detectors (in both Vertex TPCs)
Measurements show significant decrease of secondary interactions with He beam pipes installed
Position of the reconstr. interaction point along the beam direction
p+p collisions at 158 GeV
Without He beam pipes
With He beam pipes

15. Projectile Spectator Detector (PSD) 2011 ↗
120 cm
Total weight ~ 17 tons!
2011
Precise measurement of the energy
of projectile spectators.. Needed for
centrality selection (on trigger level)
measurement of event-by-event fluctuations (to reduce Npart fluctuations)
Reconstruction of the reaction plane
Resolution of 1 nucleon (!) in the studied energy range
Main features of PSD:
high energy resolution ~55%/E
high granularity: transverse homogeneity of energy resolution, reaction plane measurements
NA61 PSD central modules

16. Compensating calorimeter Pb/scintillator (4/1) sandwich
Modules 10 x 10 x 120 cm3 and 20 x 20 x 120 cm3
44 modules
now: 32 modules
(16 small and 16 large)
120 cm
120 cm
40A GeV, 23 m A GeV, 23 m A GeV, 23 m
40A GeV, 17m
(from the target)
Ready for 2011 Be run (40A, 80A, 158A GeV); 32 available PSD modules are enough
Remaining modules will be finished in 2012 (for 13A, 20A, and 30A GeV Be+Be interactions)

17. Acceptance » 50% at pT  2.5 GeV/c Tracking efficiency  95%
Pilot run in 2007 (p+C at 31 GeV) – detector fulfills the physics requirements
dE/dx versus momentum
Acceptance » 50% at pT  2.5 GeV/c
Tracking efficiency  95%
s(p)/p2 » 10-4 ((GeV/c)-1)
Extended ToF acceptance at low momenta (» 1 GeV/c)
TOF-L/R: s(t) » 60 ps
ToF-F: s(t) » 120 ps
s(dE/dx)/<dE/dx> » 0.04
s(minv) » 5 MeV
3 < p < 4 GeV/c p p K K
p,e e p

18. p- spectra in p+C at 31 GeV Rapidity spectrum 30A GeV 0 5 10 15
Pb+Pb points divided by the number of wounded projectile nucleons
PR C77, (2008)
30A GeV
F (GeV½)
p+C rapidity spectrum is shifted towards target rapidity with respect to Pb+Pb due to the projectile-target asymmetry of the initial state
NA61 p+C results at the energy of the onset of deconfinement confirm approximate proportionality of the pion yield to the mean number of wounded nucleons

19. Transverse mass spectrum of p-
0 < y < 0.2
Shape of transverse mass spectra at mid-rapidity changes from a convex form in p+C to a concave one in central Pb+Pb (with respect to corresponding exponential fits)
According to hydrodynamical approach this is due to strong radial collective flow in Pb+Pb collisions, which is absent in p+C interactions

20. Inverse slope parameter of mT spectrum of p-
Transverse mass spectra fitted with:
A exp (mT/T)
at 0.2 < mT - mp < 0.7 GeV
p+C at 31 GeV → T=151±3 MeV
Pb+Pb at 30A GeV → T=157±2 MeV
[MeV]
Pb+Pb
Inverse slope parameter increases with the collision energy, and the number of wounded projectile nucleons
p+C

21. L and K0s measurement in p+C at 31 GeV
0.4 < pT < 0.6 GeV/c
-1.25 < y < 1
pT < 0.2 GeV/c
1 < y < 1.5
Invariant mass [GeV/c²]
Invariant mass [GeV/c²]
PRELIMINARY
Armenteros-Podolansky plot after application of the V0 selection cuts. p-+C interactions at 350 GeV

22. D++ signal in p+C at 31 GeV D++ PRELIMINARY PRELIMINARY
Invariant mass of D++ → p+ p
Mass identification using the energy loss measurement in the TPC and time of flight in TOF detectors
PRELIMINARY p K+ p+ e+
D++
all accepted
PRELIMINARY

23. Event-by-event fluctuations (multiplicity, average pT)
in p+C at 31 GeV
all charged
(Target-in)
no rapidity cuts
all charged
(Target-in)
The results (next pages) are corrected for the effect of contamination from non-target interactions (both “Target-in” and “Target-out” p+C interactions were registered). For the complete procedure see Cetner, Grebieszkow, arXiv: (CPOD 2010)
The results are given in the acceptance as shown in the plots above

24. Multiplicity fluctuations in p+C at 31 GeV
neg. charged
pos. charged
all charged
Results uncorrected for on-line and off-line event selection biases
𝑁 = 𝑁 ⋅𝑃 𝑁 𝑉 𝑁 = 𝑁 2 − 𝑁 2 scaled varianceω= 𝑉 𝑁 𝑁
Multiplicity distributions for all three charge combinations are close to Poisson one
The correction for non-target interactions affect w strongly (12% for all charged, 5% for neg. charged and 10% for pos. charged)
w (all charged) = 1.08 ± 0.03 (stat)
w (neg. charged) = 0.93 ± 0.03 (stat)
w (pos. charged) = 0.83 ± 0.03 (stat)
Results from p+p energy scan (6 energies) will appear soon

25. Average pT fluctuations in p+C at 31 GeV
𝑀 𝑝 𝑇 = 1 𝑁 𝑖=1 𝑁 𝑝 𝑇 𝑖
all charged
neg. charged
pos. charged
Events with zero accepted particle multiplicity are not taken into account
Pb+Pb at 30A GeV,
forward rapidity
PR C79, (2009)
Results uncorrected for on-line and off-line event selection biases
The width of the M(pT) distribution strongly decreases with increasing colliding system size as expected from the increasing particle multiplicity
The same effect when going p+p → Si+Si → Pb+Pb at 158A GeV (see PR C70, (2004))

26. Average pT fluctuations in p+C at 31 GeV
𝑧 𝑝 𝑇 = 𝑝 𝑇 − 𝑝 𝑇 ˉ ; 𝑝 𝑇 ˉ − inclusive average event variable 𝑍 𝑝 𝑇 = 𝑖=1 𝑁 𝑝 𝑇,𝑖 − 𝑝 𝑇 ˉ Φ 𝑝 𝑇 = 𝑍 𝑝 𝑇 𝑁 − 𝑧 𝑝 𝑇 2 ˉ
Results uncorrected for on-line and off-line event selection biases
FpT (all charged) = 9.35 ± 0.15 (stat) MeV/c
FpT (neg. charged) = 1.60 ± 0.15 (stat) MeV/c
FpT (pos. charged) = 1.81 ± 0.16 (stat) MeV/c
Stronger correlation for “all charged” combination? Same observed in UrQMD
The correction for non-target interactions is very small: 0.3% (all charged), 1.6% (neg. charged) and 0.6% (pos. charged)
In UrQMD no NA61 acceptance filter applied (yet)
Estimated systematic errors are not higher than MeV/c (depending on charge combination)
Results from p+p energy scan (6 energies) will appear soon

27. The NA61/SHINE ion program gives the unique opportunity to study exciting physics in a very efficient and cost effective way
It will be complemented by the efforts of other international and national laboratories, FAIR, JINR and BNL and by the heavy ion program at the CERN LHC
CP – critical point
OD – onset of deconfinement, mixed phase, 1st order phase transition
HDM – hadrons in dense matter
PDM – properties of deconfined matter

28. Programs complementary to NA61/SHINE (2011 update)
New period in the
experimental study of
A+A collisions at the SPS
energy range started
in 2009 with the p+p
energy scan of NA61/SHINE
at the CERN SPS
RHIC Beam Energy Scan program began last year.
We look forward to the
start of the corresponding
programs at NICA
and FAIR as well as to
data from the CERN LHC

29. Summary
NA61/SHINE is a large hadron spectrometer at the CERN SPS performing measurement for three different programs:
Critical point and onset of deconfinement (ion program)
Neutrino physics
Cosmic-ray physics
Ion program:
Data already taken: p+p at 13, 20, 31, 40, 80, and 158 GeV
Numerous detector upgrades needed for data taking with ion beams are completed
The run with Be+Be will start next week (in A, 80A, 158A GeV Be+Be collisions will be registered). It will be the first NA61 run with ions and first with secondary ion beams
Be+Be, Ar+Ca, Xe+La at all 6 energies will be taken by the end of 2015
Results on p+C at 31 GeV:
y-distribution of pions: yields at 31 GeV increase approximately in proportion to projectile wounded nucleons (WNM works)
Inverse slope parameter of transverse mass pion spectra increases significantly from p+C to Pb+Pb and from 31 to 158 GeV
First results on K0s, L, D++ were obtained
Event-by-event multiplicity and average pT fluctuations were measured for the complete rapidity range available in NA61

30. NA61/SHINE Collaboration
KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary
The Universidad Tecnica Federico Santa Maria, Valparaiso, Chile
Faculty of Physics, University of Warsaw, Warsaw, Poland
Faculty of Physics, University of Sofia, Sofia, Bulgaria
Karlsruhe Institute of Technology, Karlsruhe, German
Joint Institute for Nuclear Research, Dubna, Russia
Warsaw University of Technology, Warsaw, Poland
Fachhochschule Frankfurt, Frankfurt, Germany
Jan Kochanowski University in Kielce, Poland
University of Geneva, Geneva, Switzerland
University of Belgrade, Belgrade, Serbia
Jagiellonian University, Cracow, Poland
University of Silesia, Katowice, Poland
University of Athens, Athens, Greece
ETH, Zurich, Switzerland
University of California, Irvine, USA
University of Bern, Bern, Switzerland
University of Bergen, Bergen, Norway
University of Wrocław, Wrocław, Poland
Rudjer Boskovic Institute, Zagreb, Croatia
University of Frankfurt, Frankfurt, Germany
Institute for Nuclear Research, Moscow, Russia
State University of New York, Stony Brook, USA
LPNHE, University of Paris VI and VII, Paris, France
National Center for Nuclear Studies, Warsaw, Poland
St. Petersburg State University, St. Petersburg, Russia
Institute for Particle and Nuclear Studies, KEK, Tsukuba, Japan
Laboratory of Astroparticle Physics, University Nova Gorica, Nova Gorica, Slovenia
139 participants from 28 institutes and 15 countries
Main contributors to the analysis shown in this talk: Antoni Aduszkiewicz & Tomasz Palczewski, Andrzej Wilczek, Mihailo Savic, Maciej Rybczyński, Tobiasz Czopowicz. Many thanks!

31. Back-up slides

32. Onset of deconfinement in NA49 (Alt et al., PR C77, 024903 (2008)
Verification of NA49 results and interpretation by STAR and ALICE
Rustamov, this conference
Kink: increased entropy
Pions measure early stage entropy. In SMES (APP B30, 2705 (1999)): <π>/Nw ~ (ndf) 1/4
Change of slope around 30A GeV; no change of slope in p+p data
Horn: decrease of strangeness carrier masses (rise → saturation) and of strangeness to entropy ratio (step down)
Sharp peak observed at 30A GeV (not seen in p+p);
Step: constant T and p in mixed phase
Inverse slope of mT spectra: strong rise at AGS, plateau at SPS, rise towards RHIC
π =1.5 π π −
STAR BES points confirm NA49 mesurements;
LHC point supports the interpretation
𝐹≃ 𝑠 𝑁𝑁

33. CP should be searched above the phase transition energy as ECP > EOD
From NA49 data EOD  30A GeV
Reaching the phase transition line (left) and hadronization and freeze-out at CP (right)
red circle
– stage after collision (QGP),
blue square – hadronization point (at gray line) at CP and immediately after hadronization freeze-out (also close to CP)
red circle
– stage after collision (QGP reached) but hadronization immediately (gray line)
blue square – freeze-out
E(CP)

34. Critical point search in NA49
System size dependence (p+p, C+C, Si+Si, Pb+Pb) of fluctuations at 158A GeV
all charged
Intermittency in p+p- pairs
(Pb+Pb)=6 fm ↘ (p+p)=2 fm (dashed), and 3 fm ↘ 1 fm (solid)
Fluctuations of
average pT
multiplicity
average azimuthal angle (?)
multiplicity of p+p- pairs
net-proton density
tend to a maximum in Si+Si (Si+A) collisions at 158A GeV
→ strong motivation for future experiments
Intermittency
in net protons
CP assumed at freezout of p+p at 158A GeV +A
(A=Si, Al, P)
+Pb +A
(A=C, N)
Grebieszkow et al., Nucl. Phys. A830, 547C-550C (2009);
Grebieszkow SQM2011 slides; Diakonov, this conference

35. Advantages NA61/SHINE project at SPS Beam Energy Scan at RHIC
2D scan of the phase diagram (energy and system size)
measurements of identified hadron spectra in a broad rapidity range, which in particular allows to obtain mean hadron
multiplicities in full phase space (at RHIC only BRAHMS measured 4π multiplicity of identified particles)
measurements of the total number of projectile spectators including free nucleons and nucleons in nuclear fragments
high event rate in the full SPS energy range including the lowest energies
low pT region accessible (pT > 5 MeV/c). Signatures of critical point should be visible mostly in the low pT region
Beam Energy Scan at RHIC
complete azimuthal acceptance (STAR)
acceptance not dependent on energy (canceling of many systematic uncertainties)

36. sdyn measure of dynamical particle
Fluctuation measures (NA49 and/or NA61):
sdyn measure of dynamical particle
ration fluctuations (K/p, p/p, K/p)
E-by-e fit of particle multiplicities required in NA49
Mixed events used as reference
s2dyn ∝ 1/NW (PR C81, (2010), arXiv: )
Scaled variance w of multiplicity distribution
Intensive measure
For Poissonian multiplicity distribution w=1
In wounded nucleon model (superposition) w(A+A) = w(N+N) + <n>wW
<n> - mean multiplicity of hadrons from a single N+N; wW - fluctuations in NW w is strongly dependent on NW fluctuations
relative width (of K/π, p/π, K/p) σ= 𝑅𝑀𝑆 𝑀𝑒𝑎𝑛 ⋅100 % σ 𝑑𝑦𝑛 =𝑠𝑖𝑔𝑛 σ 𝑑𝑎𝑡𝑎 2 − σ 𝑚𝑖𝑥𝑒𝑑 ∣ σ 𝑑𝑎𝑡𝑎 2 − σ 𝑚𝑖𝑥𝑒𝑑 2 ∣ σ 𝑑𝑦𝑛 2 ≈∣ ν 𝑑𝑦𝑛 ∣
ω= 𝑁 2 − 𝑁 2 𝑁
x measure (ZP C54, 127 (1992)) of fluctuations (x=pT, f, Q)
In superposition model x(A+A) = x(N+N)
For independent particle emission x=0
In superposition model x is independent of NW and NW fluctuations (strongly intensive)
𝑧 𝑥 =𝑥− 𝑥 ˉ ; 𝑥 ˉ − inclusive average event variable 𝑍 𝑥 = 𝑖=1 𝑁 𝑥 𝑖 − 𝑥 ˉ Φ 𝑥 = 𝑍 𝑥 2 𝑁 − 𝑧 𝑥 2 ˉ

37. 3rd moment of pT measure (pT(3))
Strongly intensive (PL B465, 8 (1999))
Intermittency in low mass p+p- pair
density fluctuations in pT space
Proper mass window and multiplicity required
Mixed events used as reference
Power-law behavior from s mode expected:
Critical QCD prediction f2 = 2/3
Φ 𝑝 𝑇 3 =  𝑍 𝑝 𝑇 𝑁  −  𝑧 𝑝 𝑇 3 ˉ  1 3
2D transv. momentum factorial moments: 𝐹 𝑝 𝑀 = 1 𝑀 2 𝑖=1 𝑀 2 𝑛 𝑖 𝑛 𝑖 − 𝑛 𝑖 −𝑝 𝑀 2 𝑖=1 𝑀 2 𝑛 𝑖 𝑝 𝑀 2 − number of cells in 𝑝 𝑇 space of di−pion 𝑝 𝑇,ππ = 𝑝 𝑇, π 𝑝 𝑇, π − 𝑛 𝑖 − number of reconstruc. di−pions in𝑖−th cell Δ 𝐹 2 𝑀 − combinatorial background subtracted (by use of mixed events) second factorial moment
Δ 𝐹 2 ~ 𝑀 2 φ 2

38. Secondary Hadron Beam Line for NA61:
p, K, π beam to NA61
produced hadrons:
( several masses,
broad p spectrum )
magnetic
spectrometer
primary p beam
from the CERN SPS
NA61 target
magnetic
spectrometer
T2 target
-selects beam of hadrons with a fixed p momentum
-further hadron identification possible by mass measurements

39. σ(Z)  0.27 σ(Z)  0.11 Z-detectors
measure charge of ions in secondary ion beams (on-line selection)
The Quartz (2.5 mm) Cerenkov
The Gas (60 cm C4F10) Cerenkov
Both detectors were tested during 2011 proton run (for Z=1)
Spectrum of photo-electrons for nuclei with Z=1 to Z=6. Data-based prediction and Geant4 simulation. Inset – ADC spectrum measured with proton beam at 158 GeV/c
Experimental ADC distribution and model predictions of the detector response for Z=4, 5, 6
σ(Z)  0.27
in the region of Be ions
σ(Z)  0.11
in the region of Be ions

40. A-detector
measures mass (tof, 140 m upstream of the target) of ions in secondary ion beam
Plastic scintillator bar 150 x 5 x 15 mm3 with light readout from both ends
The tof spectra measured during the 2010 test:
11C
σ(tof)  100 ps
12C
new A-detector
during the 2011 test
7Be
pure 7Be beam is possible
( 6Be and 8Be decay fast)

41. Low Momentum Particle Detector (LMPD)
Projectile (p, h) hits nucleons when passing through a nucleus (A). Some of hit nucleons can knock out other nucleons (“grey” nucleons). Centrality of p+A/h+A is correlated to the number of grey target protons with low momenta.
LMPD – physics objectives:
h+A interactions: low momentum (grey) particles measurement (energy and identification). Number of these slow particles is sensitive to the centrality of the collision → centrality detector
A+A interactions: backward multiplicity (if it can work in high multiplicity environment)
Fig. B. Boimska PhD thesis
Two small size TPCs with 4 absorber and 5 detection layers each

42. High pT physics: nuclear modification factor R
Not sufficient p+p and p+Pb statistic in NA49 and WA98
NA61 will study R for 13A-158A GeV
NA49 at 158A GeV
charged pions
p+Pb
central
Pb+Pb
counts/(GeV/c)
p+p 42
NA61/SHINE
NA61 program: 50M p + p i p GeV
(reference for the NA49 Pb + 158A GeV data)

43. (and 2010/2011 for 13 GeV). Calibration is nearly complete
Beginning of the ion program: p+p data registered in 2009
(and 2010/2011 for 13 GeV). Calibration is nearly complete
p+p at 13 GeV,
1M (2011) + 0.8M (2010)
p+p at 20 GeV,
2M events
p+p at 31 GeV,
3M events
p+p at 40 GeV,
6M events
p+p at 80 GeV,
4M events
p+p at 158 GeV,
4M events (2009)
~ 60M events in all years

44. Data taking plans: an overview

45. Within the NA61/SHINE ion program we plan to study:
Spectra and yields: K+/-, p+/-, (anti-)protons, (anti-)lambdas, K0s, other strange baryons and mesons, resonances (D++, K*, r0) by use of TPC dE/dx, ToF, decay topology, etc.
Multiplicity fluctuations (w and higher moments)
Transverse momentum fluctuations (FpT and higher moments)
Chemical fluctuations (sdyn will be replaced by new “identity method” -  measure; see Phys. Rev. C83, (2011))
Azimuthal fluctuations (Ff, see J. Phys.: Conf. Ser. 270, (2011))
Azimuthal correlations (D)
Nuclear modification factor
Correlations <pT> versus N
Critical fluctuations (intermittency) (see NA49 Phys. Rev. C81, (2010))
Other (HBT, flow, etc.)

46. Target: 20cm long liquid hydrogen (LH);
NA61 interaction trigger selects mostly Target interaction but small fraction of unwanted Non-Target interactions is also included (the problem mostly concerns p+p interactions)
p+p interactions in NA61
Target: 20cm long liquid hydrogen (LH);
contamination from Non-Target interactions (collisions with mylar windows, air/gas, etc.)
beam
In order to make corrections for those Non-Target interactions, NA61 acquires data also without target: EMPTY (for LH target) or OUT (for solid targets)
p+p full target interactions
p+p empty target interactions
FULL
EMPTY
Here will be presented a procedure of extracting Non-Target events for fluctuation measures

47. We will use α as a fraction of Target interactions within Full data sample:
α= 𝑛 𝑇 𝐹 𝑛 𝐹
where n FT is the number of Target interactions within Full data sample and n F is the total number of interactions within Full data sample
For an event variable W we can write:
< W >FT is what we would like to calculate in the end: event mean value for Target interactions (within Full data sample)
< W >F is what we directly calculate from Full data sample: the event mean value for whole Full data sample
< W >FNT is what we want to extract: event mean value for Non-Target interactions (within Full data sample)
𝑊 𝑇 𝐹 = 1 α 𝑊 𝐹 − 1−α 𝑊 𝑁𝑇 𝐹

48. Assumption
Event mean values for Non-Target interactions are the same within Full and Empty data samples calculated independently
As Empty data sample consists only of Non-Target interactions:
And Target interactions are only in Full data sample:
𝑊 𝑁𝑇 𝐹 = 𝑊 𝑁𝑇 𝐸
𝑊 𝑁𝑇 𝐹 = 𝑊 𝐸
𝑊 𝑇 𝐹 = 𝑊 𝑇
Event mean value for interactions on Target:
𝑊 𝑇 = 1 α 𝑊 𝐹 − 1−α 𝑊 𝐸
(*)

49. How to calculate a (using main vertex Z distribution)
𝑐= 𝑛 𝑁𝑇 𝐹 𝑛 𝑁𝑇 𝐸
Let us define
which depends on the sizes of used Full and Empty data samples
This leads to:
α= 𝑛 𝐹 −𝑐⋅ 𝑛 𝐸 𝑛 𝐹
p+p 40 GeV, uncalibrated data, small fraction of statistics; only to illustrate the method
We estimated values of c as a ratio of number of events with vertex Z position far from target
(-450cm to 100cm):
𝑐≈ 𝑛 𝐹 𝑛 𝐸 𝑣 𝑧 >−450𝑐𝑚
Empty target distribution normalized to the full target one such that their integrals above -450cm (TPC gas region) are equal

50. Scaled variance ω
ω= 𝑁 2 − 𝑁 2 𝑁
Definition:
Calculate:
α – fraction of interactions on Target within Full data sample
< N > and < N2 > independently for Full and Empty data (traditional way)
the same but for interactions on target:
ωT - scaled variance for interactions on Target:
𝑁 𝑇 = 1 α 𝑁 𝐹 − 1−α 𝑁 𝐸 𝑁 2 𝑇 = 1 α 𝑁 2 𝐹 − 1−α 𝑁 2 𝐸
ω= 𝑁 2 𝑇 − 𝑁 𝑇 𝑁 𝑇

51.  measure of fluctuations
Φ= 𝑍 2 𝑁 − 𝑧 2 ˉ
Definition:
where
x is a per-particle quantity that is a subject of  analysis (e.g. pT )
include quantities that are not event mean values, and cannot be corrected using equation (*) - see slide 14
One can rewrite the equation for  so that it only contains
averages over events
𝑍= 𝑖=1 𝑁 𝑥 𝑖 − 𝑥 ˉ = 𝑖=1 𝑁 𝑥 𝑖 −𝑁 𝑥 ˉ 𝑧=𝑥− 𝑥 ˉ
(calculated per event)
(calculated per particle)
𝑧 2 ˉ and 𝑍 2

52. where and (Liu et al., Eur. Phys. J. C8, 649 (1999);
Φ= 𝑋 2 𝑁 − 2 𝑋 𝑁𝑋 𝑁 𝑋 2 𝑁 𝑁 3 − 𝑋 2 𝑁 − 𝑋 𝑁 2
(**)
𝑋= 𝑖=1 𝑁 𝑥 𝑖 𝑋 2 = 𝑖=1 𝑁 𝑥 𝑖 2
where and (Liu et al., Eur. Phys. J. C8, 649 (1999);
Mrówczyński, Phys. Lett. B465, 8 (1999))
Every quantity with < > in equation above is an event mean value and can be corrected
using equation (*)
And also quantities that seem to be more complicated:
The above is true because every quantity between brackets < > is calculated independently for each event
Procedure highlight for  measure:
e.g. 𝑋 𝑇 = 1 α 𝑋 𝐹 − 1−α 𝑋 𝐸
𝑁𝑋 𝑇 = 1 α 𝑁𝑋 𝐹 − 1−α 𝑁𝑋 𝐸
Calculate:
α – fraction of interactions on Target within Full data sample
All < > values independently for Full and Empty data (traditional way)
All < > values for interactions on Target using equation (*)
Value of  measure for interactions on Target using equation (**)