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’

14M. van Leeuwen, Future prospects for NA61: rare probes

Extra slides

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?

18M. van Leeuwen, Future prospects for NA61: rare probes

-correlations from NA49M

. Szu

ba

, QM

09

19M. van Leeuwen, Future prospects for NA61: rare probes

Characterizing the shapes

PHENIX M. S

zub

a, Q

M0

9

20M. van Leeuwen, Future prospects for NA61: rare probes

Summary of correlation shapes

Away-side shape: no (large) energy dependence

Near-side shape: change from ‘dip’ to peak

M. S

zub

a, Q

M0

9