Dilepton analysis status

Run-10 Au+Au @ 200 GeV

Dmitry Kotov

Victor Riabov

Yuriy Riabov

(PNPI)

2

Event and track selection. Basic cuts.Dataset: Run-10 Au+Au @ 200 GeV (pro.84), run#300105-310354

Cuts: • DC deadmap (heavy-light meeting, 01/27/2011);• Track quality: 31 || 51 || 63;• |bbcvertex| < 20 cm;• Trigger:

BBCLL1(>1 tubes) || BBCLL1(>1 tubes) narrowvtx;• pT of unidentified track: 0.2 < pT < 10 GeV/c;• |zed| < 75 cm;• Ghost rejection for pairs (AN673, AN694):

if ( fabs(dzed)<6.0 && fabs( dphi - (0.13*dalpha) ) < 0.015 ) return false; if ( fabs( dphi - (0.04*dalpha) ) < 0.015 ) return false; if ( fabs( dphi - (-0.065*dalpha) ) < 0.015 ) return false;

• Cut for central support of DC and RICH (AN926).

3

DC dead map (I)DCE before DCE after

Side0

Side1

6X2, 7X2

8X1

8X1

Alp

ha

board

9X2

4

DC dead map (II)DCW before DCW after

Side0

Side1

9X2

12X1X2 13X2

8X2

4X1X2

9X28X2

13X1X2

Alp

ha

board

5

eID cuts.eID cuts:

• n0 > 3;• chi2n <= 10;• disp < 5;• |dep| < 2;• Cut for RICH ghosts (AN840):

( fabs(xphi[i] - xphi[j]) < 0.12 && fabs(xz[i]-xz[j]) < 25 );

• |emcsdphi_e| < 2 && |emcsdz_e| < 2;

Optional eID cuts:• |hbdsdphi| < 2.5 && |hbdsdz| < 2.5;• hbdcharge > 9, 12, 15, 21;

HBD EN2 removal:• 180 < atan(hbdy/hbdx) < 202.5 and hbdz > 0.

6

EMCal matchings

How to

• Accumulate TH2F’s emcdphi vs zed, emcdz vs theta for e+/e-;

• Slice into zed (theta) bins, Gaussian fit, extract centroids and sigmas;

• Fit centroids and sigmas with p0(pT)+p1(pT)*zed+p2(pT)*zed2:

• Except for the fit of emcdz mean: p0(pT) + p1(pT)*tan(zed);

• Fit p0, p1, p2 with c0+c1/pT+c2/pT2 to remove pT dependence;

emcsdphi_e = (emcdphi – centroid(zed, pT))/sigma(zed, pT)

emcsdz_e = (emcdz – centroid(theta, pT))/sigma(theta, pT)

7

EmcsdphiMean

SigmaRemove z-dependence

Remove pT dependence

p0

p1

p2

p0

p1

p2

Mean Sigma

Sigma

emcsdphi_e =

(emcdphi –centroid(zed, pT))

/sigma(zed, pT)25 pT bins, 8 EMCal sectors,

2 charges, 2 field orientations

Makes up to 800 histos!

1 sector, e+, +/- field,0.24< pT (GeV/c) <0.26

Remove z-dependence

Mean

Sigma

Mean

Sigma

Remove pT dependence

Mean

Sigma

Remove pT dependence

Mean

Sigma

p0

p1

p2

p0

p1

Sigma

p2

p0

p1

p0

Sigma

p2

p0

p1p1

p0

Sigma

p2

p0

p1

p2

p1

p0

Sigma

p2

p0

p1

Mean

p2

p1

p0

Sigma

p2

p0

p1

8

Emcsdz1 sector, e+, +/- field,0.24< pT (GeV/c) <0.26

Remove z-dependence Remove pT

dependence

Mean

Sigma

Mean

p1

p0Sigma

p2

p0

p1

emcsdz_e =

(emcdz –centroid(zed, pT))

/sigma(zed, pT)

25 pT bins, 8 EMCal sectors,2 charges, 2 field

orientationsMakes up to 800 histos!

9

Sigmalized variables

Emcsdphi, sector 1, +/- field

e+ e-

Mean Mean

SigmaSigma

Emcsdz, sector 1, +/- field

Mean

Sigma

Mean

Sigma

Mean

Sigma

Mean

Sigma

pT (GeV/c)

pT range of parameterizations from 0.1 to 4.0-4.5 GeV/c

10

E/p ratio parameterizations• Accumulate TH2F’s E/p vs pT for e+/e-

candidates;

• Slice into pT bins, Gaussian fit, extract centroids and sigmas and:

dep means and sigmas vs pT (sector 4, +/- field)

Mean, e+

Sigma, e+

Mean, e-

Sigma, e-

dep = (E/p – mean(pT))/sigma(pT)

pT

pT of the slice:0.4 – 0.5 GeV/c

11

HBD matching for e-candidatesHBD acceptance before hbd matching HBD acceptance after hbd matching

“After” histo divided to “before”

• In some phi-zed regions the probablity to have matching is unexpectedly low (~0.1-0.2). Why?

• Need to include this into simulation?

zed

phi

phi

zed

zed

phiphi = atan (hbdy/hbdx)

zed = hbdz

12

20 cm 20 cm,hbd

matching

20 cm, hbd matching,

hbd charge >9

20 cm, hbd matching,

hbd charge >12

20 cm, hbd matching,

hbd charge >15

20 cm, hbd matching,

hbd charge >21

Mass 3.10±0.01 3.10±0.01 3.10±0.01 3.10±0.01 3.10±0.01 3.10±0.01

Width 0.071±0.013 0.073±0.01 0.07±0.01 0.07±0.01 0.071±0.01 0.069±0.01S/B

(2.9-3.3)1/8 1/4 1/4 1/4 1/3 1/3

Min bias invariant mass spectra. J/psi peaks.

20 cm 20 cm, hbd matching

20 cm, hbd matching, hbd charge>9

20 cm, hbd matching, hbd charge>12

20 cm, hbd matching, hbd charge>15

20 cm, hbd matching, hbd charge>21

968.5±91.7 (9.4%) 621.5±53.4 (8.6%) 551.2±50.3 (10%)

503.4±48.3 (10%) 433.6±45.1 (10.4%) 302.9±39.1 (13%)

13

Phi and omega proto-peaks

• There are hints of peaks from omega and phi decays near 0.78 and 1.01:• Invisible without HBD!• Barely visible with HBD matching (|hbdsdphi|<2.5 && |hbdsdz|<2.5);• Best option is HBD matching + hbdcharge > 9.• Further increase of hbdcharge cut (12, 15, 21) impairs the signal.

20cm, hbd matching, hbd charge > 9

14

Low Minv issue

Red – BG (mixing) Black - FG

• How to improve FG behavior at low Minv < 0.3 GeV/c2;

Huge peak near Minv ~ 0 GeV/c2.

• BG shape doesn’t fully agree with FG;

Minv

Cou

nts

15

To do list

• Further work with analysis cuts (phiV);

• Need centrality recalibrator:

Do we have/can we use temporary centrality recalibrator?