1. Future prospects for NA61 heavy ions: rare observables
Connecting to high-energy results
M. van Leeuwen, Utrecht University
And the NA61 collaboration

2. Motivation Heavy ion collisions: study strong interactions bulk matter
Pure bulk = soft QCD, theoretically difficult
Hard-soft interplay studied at RHIC shows many unexpected results – do these effects exist at SPS energies?

3. Jet-like di-hadron correlations at RHIC
8 < pTtrig < 15 GeV
Combinatorial background
associated
pTassoc > 3 GeV 
trigger
Near side
Away side
Use di-hadron correlations to probe the jet-structure in p+p, d+Au
and Au+Au
At high pT > 4-6 GeV: Clear di-jet signature
Away-side suppression due to energy loss

4. Lowering pT: bulk response?
d+Au, 200 GeV
3.0 < pTtrig < 4.0 GeV/c
Jet-like peak
1.3 < pTassoc < 1.8 GeV/c
Au+Au 0-10%
STAR preliminary
M. Horner, M. van Leeuwen, et al
Near side
Enhanced yield in Au+Au
`Ridge’: associated yield at large 
Away-side:
Strong broadening in central Au+Au
‘Dip’ at  = 
dN/d approx. independent of 
Large modifications of di-hadron structure at intermediate pT
Modified fragmentation? Bulk response?

5. Comparing SPS and RHIC
M. Szuba
SPS full energy: di-hadron structure similar to RHIC, yields lower  lower jet energy

6. Energy dependence of di-hadron correlations at SPS
M. Szuba
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?

7. Charm production at RHIC
STAR, PRL 98 (2007)
J. Dunlop, QM09
pQCD expectation
Suppression at high-pt: charm interacts with medium
Total cross section scales with Ncoll
Q: does charm thermalise? Measure charm spectra at low pt, v2
Requires upgrades ~10M$ for STAR and PHENIX at RHIC

8. Charm with NA61?
NA49: D0 K p
N(D0+D0) =  0.74 per event
N(D0+D0) < 1.5 per event (C.L. 98%)
3.8M events
Phys.Rev.C73:034910,2006
Expected yields:
1 year running of NA61 ~300M events would give 3s
 Need vertex detector

9. Technology candidate: GOSSIP
H. van der Graaf et al., NIKHEF
GOSSIP
GridPix
Gas on Slimmed Silicon Pixels
Pixel readout 55x55 mm
+ time
Use time-dependence to image track in gas layer

10. Occupancy for vertex detector
2-track distance
Hits at z = 10 cm
Central Pb+Pb at 158 AGeV
For y < 4 ~ R > 0.3 cm, two-track distance ~ 300 mm
z = 10 cm safe choice for first plane

11. Vertex resolution with vertex detector
Decay distance along beam
Resolution
158 AGeV collisions
Including Mult scatt ~600 mm Si per plane
Geometry: 6 planes, 10, 15 … 40 cm
Lorentz boost: large decay lengths (mm scale)
Looks promising: typical decay length >> resolution

12. Summary of proposal 2 runs of NA61 ~8 weeks, 200-300M events
Highest SPS energy: 158 AGeV
Low energy: 20/30 AGeV
Measurement 1: jet-like di-hadron structure
Peak-dip transition, explore pT-dependence, h-j structure – connection to bulk response effects at RHIC
Measurement 2: charm production
Need vertex detector
Measure yield, pT spectra (radial flow) and v2?

13. Extra slides

14. PHENIX, PRL 98 (2007)

15. Lowering pT: gluon fragments/bulk response
d+Au, 200 GeV 
trigger
Au+Au 0-10%
STAR preliminary
Jet-like peak
associated
3 < pt,trigger < 4 GeV
pt,assoc. > 2 GeV
Long. flow
J. Putschke, M. van Leeuwen, et al
`Ridge’: associated yield at large 
dN/d approx. independent of 
Strong - asymmetry suggests effect of longitudinal flow or underlying event

16. More medium effects: away-side
Mach Cone/Shock wave
T. Renk, J. Ruppert
Stöcker, Casseldery-Solana et al
3.0 < pTtrig < 4.0 GeV/c
1.3 < pTassoc < 1.8 GeV/c
Trigger particle
Au+Au 0-10%
A. Polosa, C. Salgado
Gluon radiation +Sudakov
d+Au
M. Horner, M. van Leeuwen, et al
Medium response (shock wave) or gluon radiation with kinematic constraints?
Near side:
Enhanced yield in Au+Au consistent with ridge-effect
(other proposals exist as well: kT-type effect or Cherenkov radiation)
Away-side:
Strong broadening in central Au+Au
‘Dip’ at  = 
Note also: not shown is large background – something non-trivial may be hiding there?

17. Dj-correlations from NA49
M. Szuba, QM09

18. Characterizing the shapes
PHENIX
M. Szuba, QM09

19. Summary of correlation shapes
M. Szuba, QM09
Away-side shape: no (large) energy dependence
Near-side shape: change from ‘dip’ to peak