chic @ sps ( charm in heavy ion collisions)

Frédéric Fleuret - LLR 1

Chic @ SPS(Charm in Heavy Ion Collisions)

Detector designA 3rd generation experiment to study charm with

proton and ion beams on fixed target at SPS


Physics motivations – 2 key questions

1. Measure cc in A+AUnderstanding similar J/Y suppression observed at SPS and RHIC:

1. Either more suppression at RHIC compensated by recombination2. Or J/Y suppression due to cc only sequential suppression

How cc is suppressed relative to J/Y ? What is the dependence with y, pT, Npart,… ?

Mandatory to draw the whole picture (SPS .vs. RHIC .vs. LHC)

2. Measure charmonia production in p+Awhat is the depence of charmonia suppression with rapidity ?Crucial to understand effects due to cold nuclear matter


1. Measure cc in A+AEur. Phys. J. C49 (2007) 559

NJ/Y ~ 60% direct + ~30% from cc + ~10% from Y’

Phys. Rev. Lett. 99, 132302 (2007)

cc

Suppression?

Direct J/YSuppression

?

Benchmark: measure cc in PbPb• at mid-rapidity

NA50 NA60

Y’

cc ??Direct J/ ??Y

http://dx.doi.org/10.1103/PhysRevLett.99.132302






2. Measure charmonia in p+A

Euro. Phys. J. C48 (2006) 329.

J/Y and Y’ suppression in p+A collisions as a function of L

Measuring different charmonium states gives key information on nuclear « absorption » and production mechanism.

J/Y rapidity distribution in p+A collisions (asymetry wrt ycm=0)

Measuring charmonium in a wide xF range is important to identify possible (anti)shadowing effects

NA50

Y’

J/Y

http://www.springerlink.com/content/nrm134800q0p771k/?p=5e77140a5d0c47149f22669235120b29&pi=1


2. Measure charmonia in p+A

Possible to access large xF if measuring charmonia at rapidity up to y*~2

*sinh2

ys

MxF

With M=3.1 and s=17.2 GeV (158 GeV)xF = 1 y* = 1.7

With M=3.1 and s=29.1 GeV (450 GeV)xF = 1 y* = 2.2Y*=2 xF = 0.8

E866, Phys. Rev. Lett. 84, 3256-3260 (2000)

Measuring charmonium in a wide xF range is important to identify possible (anti)shadowing effects


Experimental landscape• Current landscape

– Fixed target : SPS/CERN NA38/50/60 experiments – sNN = 17 – 30 GeV• Statistics :100 000’s J/y• Data sets : p+A w/ A=p, d, Be, Al, Cu, Ag, W, Pb; S+U, In+In, Pb+Pb• Small rapidity coverage (typically y [0,1])

– Collider : RHIC/BNL Phenix, Star experiments – sNN = 200 GeV• Statistics : 1000’s J/ y (10000’s since 2007)• Data sets : p+p, d+Au, Cu+Cu, Au+Au• Large rapidity coverage (y [-0.5,0.5], y [-2.2,-1.2] and y [1.2,2.2])

– Collider : LHC/CERN Alice, CMS, Atlas experiments (sNN = 5,5 TeV)• Statistics : 100000’s J/y• Data sets : p+p, Pb+Pb, p+Pb• Large rapidity coverage (|y|<2.5 ATLAS/CMS, |y|<0.9 and -4.0 < y < -2.5 ALICE)

• Feedback : 4 key points1. High statisticsdraw clear suppression pattern in Hot Nuclear Matter and Cold Nuclear Matter2. Large data set draw clear suppression pattern in Cold Nuclear Matter3. Large xF (rapidity) coverage understand suppression mechanism in Cold Nuclear Matter

4. As large sample of quarkonium states as possible understand suppression mechanism in Hot Nuclear Matter and Cold Nuclear Matter


Expected yield

• Need high intensity p and Pb beams (~ 107 Pb/sec)• NA50/NA60 beam line not available (NA62)• H2 beam line occupied by NA61• H4 and H8 available but need shielding for HI

• NA50: European Physical Journal C39 (2005) 335 • New measurement of J/y suppression in Pb+Pb at 158 GeV/nucleon • 35 days of data taking in 2000• ~1.107Pb/s over 5s bursts every 20s• 4 mm thick Pb target (10%lI) • ~ 100 000 J/Ym+m- within y*[0,1] (on tape)

• Expect fair amount of cc: NJ/Y ~ 60% direct + ~30% from cc + ~10% from Y’ • With same conditions as 2000 NA50 setup ~30 000 cc expected (asuming same acceptance)• Expect more with larger y* range• Expect more with thicker target (1cm for instance)

North Area Beamlines


NA38, NA50, NA51: 1st generation

Fixed target experiments

Active Target absorber spectrometer muID

Active target, but no vertex for open charm and not very good mass resolution


Fixed target experimentsNA60: 2nd generation

Active Target telescope absorber spectrometer muID

+ NA50

See NA50

Active target, vertex for open charm and not very good mass resolution


CHIC: 3rd generation

Active target vertex spectrometer calorimeter absorber muID

Fixed target experiments

Dipole field

Muon Filter(absorber)

target

vertex

tracking tracking

MuID

Beam

EMCal

Active target, vertex for open charm, calorimeter for cc and very good mass resolution


Detector – tracking• The NA60 example

Pixel detector• 16 planes – 96 chips total• 32 x 256 pixels / chip• Pixel size = 425 × 50 mm²•Magnetic field = 2.5 T × 40 cm

Momentum resolution @J/Y mass

(typical pm ~ 15 GeV/c)

%6~P

P

(R. S. priv. Comm.)


Detector – tracking • NA60 pixel momentum resolution (R.S. priv. Comm.)

MeV 130~%2.42

%6 /

JMP

P

M

M

P

P

PBP

P

3.0

4

320

²

NLres

(Particle Data Group, NIMA 410, 284-292 (1998))

r = curvatureB = magnetic fielde = measurement errorN = number of points measuredL = projected length of the track onto the bending plane

Major parameters for improvement :Magnetic field and measurement error (linearly)Length into magnetic field (quadratically)

0~MS

~40 cm

222MSres

B (T) L (cm) e(imp.)

DP/P (%)

DM (MeV)

2.5 40 ×1 ~ 6 ~130

2.5 60 ×1 ~ 2.7 ~60

2.5 80 ×1 ~ 1.5 ~30

2.5 100 ×1 ~1 ~20

NA60

LB=40 cm LB=100 cm DP/P ~1% DMJ/Y ~ 20 MeV

PBLP

P2

1

Magneticfield Magnet

length


Detector – tracking • Size, position, resolution : tentative design – toy example

B (T) L (cm) DP/P (%)

DM (MeV)

2.5 40 ~ 6 ~120

2.5 60 ~ 2.7 ~60

2.5 80 ~ 1.5 ~30

2.5 100 ~1 ~20

NA60

6 plane vertex@ rmin = 0.5 cm zmin(h*=0.5)~7.5 cm6 planes from z=8 cm to z=18 cm

*h=-0.5

*h =0.5

*h =1

11 plane spectrometer@ zmax = 120 cm rmax(h*=-0.5)~22 cm11 planes from z=20 cm to z = 120 cm

*h=-0.5

*h =0.5

CHIC 22

7.5Track particles within h*[-0.5 ; 1]


Detector – tracking • Size, position, resolution : tentative design – toy example

B (T) L (cm) DP/P (%)

DM (MeV)

2.5 40 ~ 6 ~120

2.5 60 ~ 2.7 ~60

2.5 80 ~ 1.5 ~30

2.5 100 ~1 ~20

NA60

6 plane vertex@ rmin = 0.5 cm zmin(h*=0.5)~7.5 cm6 planes from z=8 cm to z=18 cm

*h=-0.5

*h =0.5

CHIC

7.5Track particles within h*[0.5 ; 2]

11 plane spectrometer@ zmax = 120 cm rmax(h*=-0.5)~22 cm11 planes from z=100 cm to z = 200 cm

*h =0.5

*h =2

22


Detector – tentative design

20 cm

40 cm

60 cm

80 cm

100 cm

120 cm

1 m 3 m 4 m 5 m 6 m2 m

Vertex detector :Rmin = 0.5 cm Zmin = 7.5 cmRmax = 3.5 cm Zmax = 18 cm

Spectrometer :Rmin = 1 cm Zmin = 20 (100) cmRmax = 22 cm Zmax = 120 (200) cm


• Goal : measure the photon from cc J/Y + g

• Issues1. Low energy photon (similar to p0 gg)2. High multiplicity of photon from p0 /h gg3. High multiplicity of charged particles (p+/-)

Detector – calorimetry

<pT>~500 MeV <E>~3 GeV

Pythia 6.421 - p+p - s = 17.2 GeV


• Goal : measure the photon from cc J/Y + g

• Issues1. Low energy photon (similar to p0 gg)2. High multiplicity of photon from p0 /h gg3. High multiplicity of charged particles (p+/-)

Detector – calorimetry WA98: Phys. Lett. B458: 422-430, 1999)

Phobos: Phys. Rev. C74, 021901, 2006

~500 g

~340 g

~350 p+/-

Epos 1.6 : Pb+Pb @ 17.2 GeV

~400 g

~370 p+/-

0 – 5%

0 – 5%

0 – 5% Pb+Pb most central ~500 g + 400 p+/-

(we don’t need to go that central for cc)Epos 1.6 : Pb+Pb @ 17.2 GeV


• Need very high segmentation– to separate two electromagnetic showers– To isolate photons from p+/- contamination

• W + Si calorimeter à la Calice– 30 layers– 0.5 x 0.5 cm2 pads– 24 X0 in 20 cm

• W+Si : two relevant quantities

Detector – calorimetry

1st relevant quantity : distance between two incoming particles

Min. distance between 2 particles at impact = 1 free pad = 1 cm (for 0.5×0.5 cm²)distance between two incoming particles must be > 1 cm N photons N/2 neutrals (p0 + h) N p+/- N g + N p+/- = 2N particles distance between two photons must be > 2 cm (1cm×2N/N)

bad good

2nd relevant quantity : EM shower transverse size Moliere Radius RM : 90% of the shower energy

Distance between two photons must be > 2 cm (2 RM)

cm 0.9

g.cm 19.25

g.cm 17.6WR

Z2871)lnZ(Z

g.cmA 716.4X

1.24ZMeV 610

MeV 21XR

3

2

M2-

0

0M

Geometrical condition: in principleDg > 2cm


Detector – calorimetry• Size and position : tentative design

Dg>4

<Dg 2<Dg 1

Dg>2

[-0.5:0.5]rmin

rmax

Z

20 cm

0 – 5% most central Pb+Pb events as measured by WA98

200500

d

dN

),(

)²,()²,(2

maxmin

maxmin

N

zrzr Distance between

two photons

Closer position to the target w/ Dg>2cm:Z = 205 cm [-0.5:0.5]

Rmin = 13.6 cmRmax = 40.9 cm

Using 0.5 x 0.5 cm² pads


Detector – calorimetry• Size and position : alternative design

rmin

rmax

Z

20 cm

Warning : not clear that Dg>2 cm is large enough; for instance, RM (W+Si) > RM(W). Try alternative design:taking Dg>4cm with z = 205 cm, Rmin=30 cm, Rmax= 55cm h* [-0.8, -0.3] loose some cc acceptance, but safe !!!Must check with full simulation what is optimum Dg !

Dg>4

Dg>2

<Dg 2



20 cm

40 cm

60 cm

80 cm

100 cm

120 cm

1 m 3 m 4 m 5 m 6 m2 m

Vertex detector :Rmin = 0.5 cm Zmin = 7.5 cmRmax = 3.5 cm Zmax = 18 cm

Spectrometer :Rmin = 1 cm Zmin = 20 (100) cmRmax = 22 cm Zmax = 120 (200) cm

Calorimeter Dg>2 cm: acceptance 1Rmin = 14 cm Zmin = 205 cmRmax = 41 cm Zmax = 225 cm


hg* [-0.5, 0.5] hg* [-0.8, -0.3]


Performances in p+p• Pythia 6.421 – p+p – s = 17.2 GeV

– 20 000 generated events• Include DP/P=1%• Include DE/E=20%/E

PYTHIA 6.42120000 events

Y*=0 YCMS~2.92

AJ/Y~18.4%

Ac~8.5%

Acceptance 12 m from J/Y in -0.5<y*<0.5

1 g from cc

in -0.5<y*<0.5

Ac~3.2%

AJ/Y~18.4%

Acceptance 22 m from J/Y in -0.5<y*<0.5

1 g from cc

in -0.8<y*<-0.3


Performances in p+p – acceptance 1• Pythia 6.421 – p+p – s = 17.2 GeV : 20 000 generated events

2 m from J/Y within -0.5<y*<0.51 g from cc within -0.5<y*<0.5


Performances in p+p – acceptance 2• Pythia 6.421 – p+p – s = 17.2 GeV : 20 000 generated events

2 m from J/Y within -0.5<y*<0.51 g from cc within -0.8<y*<-0.3


Standard design Alternative design

Performances in p+p

-0.5< y*(m)<0.5 -0.8<y*(g)<-0.3-0.5< y*(m)<0.5 -0.5<y*(g)<0.5

J/Y J/Y

cccc


m

p+

DHCal

http://newsline.linearcollider.org/archive/2010/20101104.html

Detector – absorber • Absorber type

NA50/NA60 : measure muon momentum after the absorber must minimize multiple scattering

– Must use low Z material: best = BeO (but expensive)– NA50 : 0.6 m BeO + 4 m C + 0.6 m Fe = 5.2 m

CHIC : measure muon momentum before the absorber minimization of multiple scattering less crucial can use Fe material To absorb p+/-

Need to match muon track position between spectrometer and trigger : Use an instrumented Fe absorber

Can match muon track momentum between spectrometer and trigger : Use magnetized Fe absorber ?

Minos


Detector – absorber • Pion absorption and muon energy loss

GeV 3.5μP

GeV 4.4πP

/L

/L

0.3

50 GeV/c

p+/- momentum up to ~50 GeV/c

At least 2 m Fe length neededFraction of hadron energy absorbed in Fe

All p+/- stopped with a ~2.0 m Fe absorber


Detector – absorber • Pion absorption and muon energy loss

dE/dx ~ 2 MeV g-1 cm2

Fe density ~ 7.8 g cm-3 dE/dx ~ 15.6 MeV cm-1

Muon energy loss in Fe

All p+/- stopped with a 2.0 m Fe absorberbut need more Fe to stop muons from pion decay 2.0 m Fe DE/Dx ~ 15.6 x 200 ~ 3.1 GeV AJ/Y ~ 18.4 % 3.2 m Fe DE/Dx ~ 15.6 x 320 ~ 5 GeV AJ/Y ~ 18.0 % 3.8 m Fe DE/Dx ~ 15.6 x 380 ~ 6 GeV AJ/Y ~ 17.3 % 4.5 m Fe DE/Dx ~ 15.6 x 450 ~ 7 GeV AJ/Y ~ 16.1 %

3 5 7


• Pb Beam intensity– NA50 5.107 ions/bunch 107 ions/sec (with a bunch time length ~ 5 sec)– Luminosity : L = Nb x NT = Nb x ( r x e x NA)/A = 107x(11.35 x 1 x 6.02 1023)/207.19 = 0.3 mb-1s-1

• Number of min bias events (for Pb+Pb)– sI=68.8 x (A1/3

proj + B1/3targ – 1.32)2 sPbPb

minbias=68.8 x (2081/3 + 207.191/3 – 1.32)2=7.62 barn– Nevents/sec ~ 0.3 106 x 7.62 ~ 2.3 MHz

• Event rejection :

Detector – trigger rate in Pb+Pb

10 000 Pb+Pb minbias eventsgenerated with EPOS 1.6

At least 2 m in theDetector (44 events)

3.2m Fe abs.: Pz>5 GeV/c: Trigger accepts 44/10000 events Nevents/sec ~ 2.3 MHz x 4.4 10-3 ~ 10 kHz3.8m Fe abs.: Pz>6 GeV/c: Trigger accepts 12/10000 events Nevents/sec ~ 2.3 MHz x 1.2 10-3 ~ 2.8 kHz4.5m Fe abs.: Pz>7 GeV/c: Trigger accepts 3/10000 events Nevents/sec ~ 2.3 MHz x 3 10-4 ~ 700 Hz

cm 215ZGeV/c 6P

5.0y0.5-

μvertex

μz

*

At least 2 m in theDetector (12 events) At least 2 m in the

Detector (3 events)At least 2 m in theDetector (329 events)

cm 215ZGeV/c 7P

5.0y0.5-

μvertex

μz

*

cm 215ZGeV/c 5P

5.0y0.5-

μvertex

μz

*

cm 215ZGeV/c 3.1P

5.0y0.5-

μvertex

μz

*

Absorber starts @ 205 cm p+/- stop decaying after 1 lI in tungsten (lI~10cm) p+/- stop decaying @ 2.15 m



20 cm

40 cm

60 cm

80 cm

100 cm

120 cm

1 m 3 m 4 m 5 m 6 m2 m

Vertex detector :Rmin = 0.5 cm Zmin = 7.5 cmRmax = 3.5 cm Zmax = 18 cmSpectrometer :Rmin = 1 cm Zmin = 20 (100) cmRmax = 22 cm Zmax = 120 (200) cm



hg* [-0.5, 0.5] hg* [-0.8, -0.3] 1 m 3 m 4 m 5 m 6 m2 m

2.5 cm

7.5 cm


Performances• Test performances with tentative design

– Detector design: test two setups1. Standard design : -0.5<y*(m)<0.5 | PZ(m)>7 GeV | zvertex(m)<215cm| -0.5<y*(g)<0.5

2. Alternative design : -0.5<y*(m)<0.5 | PZ(m)>7 GeV | zvertex(m)<215cm| -0.8<y*(g)<-0.3• Trig events w/ 2 muons from J/Y within acceptance

– Event sample : p+p @ s = 17.2 GeV• 20 000 cc2 events generated with Pythia 6.421 • Muon momentum smeared with DP/P=1%• Photon energy smeared with DE/E=20%/E

– Event sample : Pb+Pb @ s = 17.2 GeV• 10 000 minBias events generated with Epos 1.6• 1 pythia cc2 (2 m+ 1g) embedded in each Pb+Pb event• Muon momentum smeared with DP/P=1%• Photon energy smeared with DE/E = 20%/E



Performances in p+p

-0.5< y*(m)<0.5 -0.5<y*(g)<0.5Pz (m) > 7 GeVzvertex(m)<215 cm

S/B(J/Y )~no Bkg S/B(cc )~1.2

-0.5< y*(m)<0.5 -0.8<y*(g)<-0.3Pz (m) > 7 GeVzvertex(m)<215 cm

S/B(J/Y )~no Bkg S/B(cc )~0.9



Improve p+p S/B

Apply a cut on Mgg:Reject all photon pairs belonging to Mgg [100 MeV, 160 MeV] (Mp0 = 135 MeV)

Mgg

Mgg(p0)

Mgg(1 g from cc)

S/B(J/Y )~no Bkg S/B(cc )~1.2S/B(J/Y )~no Bkg S/B(cc )~2.8


• With no cut:• S/B > 1 for standard design• S/B > 0.5 for alternative design

• With Mgg cut:• S/B ~ 3 for standard design• S/B > 1 for alternative design

• No problem to measure cc in p+p. Shouldn’t be a problem in p+A

Performances in p+p – conclusion

3229 events/200001170 cc

Standard designS/B~2.8

3229 events/20000429 cc

Alternative designS/B~1.2



Performances in Pb+Pb minBias

-0.5< y*(m)<0.5 -0.5<y*(g)<0.5Pz (m) > 7 GeVzvertex(m)<215 cm

S/B(J/Y )~11 S/B(cc )~0.035

-0.5< y*(m)<0.5 -0.8<y*(g)<-0.3Pz (m) > 7 GeVzvertex(m)<215 cm

S/B(J/Y )~11 S/B(cc )~0.024



Performances in Pb+Pb minBias

-0.5< y*(m)<0.5 -0.5<y*(g)<0.5Pz (m) > 7 GeV 100 < Mgg < 160 MeVzvertex(m)<215 cm

S/B(J/Y )~11 S/B(cc )~1.7

-0.5< y*(m)<0.5 -0.8<y*(g)<-0.3Pz (m) > 7 GeV 100 < Mgg < 160 MeVzvertex(m)<215 cm

S/B(J/Y )~11 S/B(cc )~0.44



Improve S/B in Pb+Pb

S/B(J/Y )~11 S/B(cc )~3.6

J/Y

g

J/Y g

Oppositehemisphere

Samehemisphere

Apply a cut on cosq Reject all photons with cosq<0

cosq

qq

S/B(J/Y )~11 S/B(cc )~0.9

J/Y

g

J/Y g

Oppositehemisphere

Samehemisphere

cosq

qq


• In Pb+Pb minBias:– With no cut : S/B ~ 0.01 for both design– With Mgg cut and angular cut : S/B ~ 3.6 (0.9) for standard (alternative) design

• Measuring cc photons in -0.5 < y* < 0.5 is the best solution– Dg = 2 cm may be challenging, but we can reduce this constraint by:

• Finding a compromise between -0.5 < y* < 0.5 and -0.8 < y* < -0.3• Shifting the detector to a larger z

– Note that Dg=2cm correspond to y*=0.5 for 0 – 5% most central Pb+Pb.

Performances in Pb+Pb – conclusion

1596 events/10000107 cc

Standard designS/B~3.6

alternative designS/B~0.9

1596 events/1000060 cc


Conclusion• Measuring cc, J/Y, Y’, open charm production in Pb+Pb needs :

– Very good muon momentum resolution– High granularity calorimeter– Efficient trigger

• New technologies used to design a 3rd generation detector– 2.5 T magnetic field along 1m– Si vertex detector, Si spectrometer– W+Si EMCal– Fe DHCal– Magnetized Fe absorber

• Results– J/Y (Y’) measurement: Excellent performances expected– cc measurement:

• Good performance in p+p • Good performance in Pb+Pb minBias ok for peripheral and mid-peripheral• Mid-central and central collisions collisions may be an issue. Need to perform more simulations to

optimize the detector and analysis.


backup


Experimental challenges4 key points

2. Large data setDraw clear suppression pattern in CNM

NA50, Euro. Phys. J. C48 (2006) 329

Study P+Be, Al, Cu, Ag, W, Pb

Using several targets is a key element to study quarkonia suppression in Cold Nuclear Matter

At RHIC the study of CNM with d+Au suffered from the poor centrality resolution

PHENIX, arXiv:1010.1246

RT=transverse radial position of the N-N collision relative to the center of the gold nucleus

http://www.springerlink.com/content/nrm134800q0p771k/?p=5e77140a5d0c47149f22669235120b29&pi=1



3. Large xF coverage in p+A

Having a large xF coverage is a good point to study quarkonia suppression in Cold Nuclear Matter

*sinh2

ys

MxF

With M=3.1 and s=17.2 GeV (158 GeV)xF = 1 y* = 1.7

With M=3.1 and s=29.1 GeV (450 GeV)xF = 1 y* = 2.2Y*=2 xF = 0.8

E866, Phys. Rev. Lett. 84, 3256-3260 (2000)



3. Large sample of quarkonia statesH. Satz, J. Phys. G 32 (2005)

NA50, Eur. Phys. J. C49 (2007) 559

Y’

cc

J/Y

NJ/Y ~ 60% direct + ~30% from cc + ~10% from Y’

chic @ sps ( charm in heavy ion collisions)

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