Future prospects for NA61 heavy ions: rare observables
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Future prospects for NA61 heavy ions: rare observables
Connecting to high-energy (RHIC) results
M. van Leeuwen, Utrecht Universityand the NA61 collaboration
Workshop:New Opportunities in the Physics Landscape at CERN11-14 May 2009
2M. van Leeuwen, Future prospects for NA61: rare probes
Motivation
• Heavy ion collisions: study strong interactions bulk matter
– Identify phase transition to Quark-Gluon-Plasma
• Pure bulk = soft QCD, theoretically difficult
• Hard-soft interplay studied at RHIC shows many unexpected results – do these effects exist at SPS energies?
– Can we ‘switch off’ some effects – transition ?
3M. van Leeuwen, Future prospects for NA61: rare probes
Jet-like di-hadron correlations at RHIC
At high pT > 4-6 GeV: Clear di-jet signatureAway-side suppression due to energy loss
associated
trigger
8 < pTtrig < 15 GeV
pTassoc > 3 GeV
Use di-hadron correlations to probe the jet-structure in p+p, d+Au
Near side Away side
and Au+Au
Combinatorialbackground
STAR, PRL97, 162301
p+p event display
4M. van Leeuwen, Future prospects for NA61: rare probes
Lowering pT: bulk response?
3.0 < pT
trig < 4.0 GeV/c
1.3 < pT
assoc < 1.8 GeV/c
Near sideEnhanced yield in Au+Au
Away-side:Strong broadening in central Au+Au
‘Dip’ at =
STAR, M. Horner, M. van Leeuwen, et al
Au+Au 0-10%STAR preliminary
Jet-like peak
`Ridge’: associated yield at large dN/d approx. independent of
d+Au, 200 GeV
Large modifications of di-hadron structure at intermediate pT
Modified fragmentation? Bulk response?
ST
AR
, Pu
tschke
et a
l
3 < pt,trigger < 4 GeVpt,assoc. > 2 GeV
5M. van Leeuwen, Future prospects for NA61: rare probes
Comparing SPS and RHIC
SPS full energy: di-hadron structure similar to RHIC yields lower lower ‘jet’ energy
M. S
zub
a, H
ot Q
ua
rks 20
08
6M. van Leeuwen, Future prospects for NA61: rare probes
Energy dependence of di-hadron correlations at SPS
Qualitative change from low to high energy: from near-side dip to near-side peak
Clear turn-on as a function of energy. What is the mechanism?
M. S
zub
a, H
Q0
8
New data needed to study , pT-dependence, above and below transition
40 AGeV 20 AGeV
7M. van Leeuwen, Future prospects for NA61: rare probes
Charm production at RHIC
Low pT, RAA~ 1Total cross section scales with Ncoll as expected
Suppression at high-pt: charm interacts with medium
Does charm thermalise? Measure charm spectra at low pt, v2
Will be measured at RHIC (STAR, PHENIX upgrades)and LHC (ALICE, others?)Can we measure this at SPS? Thermalised charm at SPS?
ST
AR
, PR
L 9
8 (2
00
7) 1
92
30
1
p+pTcoll
Au+AuTAA |dpdNN
|dpdN=R
//
8M. van Leeuwen, Future prospects for NA61: rare probes
Charm with NA61?
NA49: D0 K 3.8M events
Would need ~300M events (300 days running) for 1 Need vertex detector to measure D0, pT spectra, v2
Ph
ys.Re
v.C7
3:0
34
91
0,2
00
6
N(D0+D0) = -0.36 0.74 per eventN(D0+D0) < 1.5 per event (C.L. 98%)
NA61: c + -
μb4.13.15.9 ppcc
EPJ C59, 607
N(D0+D0) expected: ~ 0.11 per central event
e.g. 20M central events gives 80k D0 K
9M. van Leeuwen, Future prospects for NA61: rare probes
Technology candidate: GOSSIP
GridPix/InGridGOSSIP
Gas on Slimmed Silicon Pixels
H. van der Graaf et al., NIKHEF
Pixel size 55 x 55 m+ time
Use time-dependence toimage track in gas layer
Thin, precise and cheap !
Gas amplification + pixel readout
10M. van Leeuwen, Future prospects for NA61: rare probes
Occupancy for vertex detector
Central Pb+Pb at 158 AGeV
Hits at z = 10 cm2-track distance
For y < 4 ~ R > 0.3 cm, two-track distance ~ 300 m
z = 10 cm safe choice for first plane
ycms < 1
11M. van Leeuwen, Future prospects for NA61: rare probes
Vertex resolution with vertex detector
Decay distance along beam Decay length resolution
158 AGeV collisions Including Mult scatt ~600 m Si per plane
Geometry:6 planes, 10, 15 … 40 cm
Lorentz boost: large decay lengths (mm scale)
Looks promising: typical decay length >> resolution
12M. van Leeuwen, Future prospects for NA61: rare probes
Summary of proposal
• 2 runs of NA61 ~10 weeks, 70M events(after baseline heavy ion program, 2014+)
– Highest SPS energy: 158 AGeV
– Low energy: 20/30 AGeV
• Measurement 1: jet-like di-hadron structure– Peak-dip transition, explore pT-dependence, - structure –
connection to bulk response effects at RHIC
• Measurement 2: charm production– Need vertex detector
– Measure yield, pT spectra (radial flow) and v2?
13M. van Leeuwen, Future prospects for NA61: rare probes
Towards a 4 detector?
• Qualitative step forward in hadron production experiments
• Goal: address unsolved issues from ISR era:– Cronin effect– Changeover/interplay soft-hard production– Baryon formation/transfer– Others?
Concept: a large acceptance detector for ‘all’ particles (EM + charged hadrons + neutral hadrons) to perform exclusive
measurements of hadron production at the SPS energy range.
SPS has the potential to address many of these issues: wide energy range and choice of beams to narrow down the ‘model space’
15M. van Leeuwen, Future prospects for NA61: rare probes
Charm production at RHIC
PHENIX, PRL 98 (2007) 172301
Total cross section scales with Ncoll
-- as expected
J. Dunlop, QM09
pQ
CD
ex
pe
cta
tion
p+p Au+Au
cc/
Nco
ll [m
b]
Remove!
16M. van Leeuwen, Future prospects for NA61: rare probes
Lowering pT: gluon fragments/bulk response
3 < pt,trigger < 4 GeVpt,assoc. > 2 GeV
Au+Au 0-10%STAR preliminaryassociated
trigger
Jet-like peak
`Ridge’: associated yield at large dN/d approx. independent of
Strong - asymmetry suggests effect of longitudinal flow or underlying event
Long. flow Long. flow
J. Putschke, M. van Leeuwen, et al
d+Au, 200 GeV
17M. van Leeuwen, Future prospects for NA61: rare probes
Trigger particle
More medium effects: away-side3.0 < p
Ttrig < 4.0 GeV/c
1.3 < pT
assoc < 1.8 GeV/c
Mach Cone/Shock wave
T. Renk, J. Ruppert
Stöcker, Casseldery-Solana et al
A. Polosa, C. Salgado
Gluon radiation+Sudakov
Au+Au 0-10%
d+Au
Near side:Enhanced yield in Au+Au consistent with ridge-effect Away-side:
Strong broadening in central Au+Au‘Dip’ at =
Medium response (shock wave)or gluon radiation with kinematic constraints?
(other proposals exist as well: kT-type effect or
Cherenkov radiation)
M. Horner, M. van Leeuwen, et al
Note also: not shown is large background – something non-trivial may be hiding there?
19M. van Leeuwen, Future prospects for NA61: rare probes
Characterizing the shapes
PHENIX M. S
zub
a, Q
M0
9
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