f0, ? , a1 with ALICE

1
f0, ?, a1 with ALICE

• Sergey Kiselev, ITEP Moscow for the TOF group
• Introduction
• Input info and assumptions
• Acceptance
• Signal and background
• pp
• AuAu
• Summary

2
Introduction
SQM07 short-lived resonances, motivation last
results
channel B.R.() c? (fm) RHIC data ?m
(MeV) ALICE studies

• a1(1260) ? p ? 0.5 0.5
• ?0(770) ? p p- 100 1.3
  pp/dA/AuAu -70 pp/AuAu
• ?(1232) ? p p 100 1.6 pp/dAu
  -40
• f0(980) ? p p- 66 2.6
  pp/AuAu
• K(892) ? p K 100 4
  pp/dAu/AuAu -10 pp/AuAu
• S(1385) ? ? p 88 5.5
  pp/dAu/AuA 0
• ?(1520) ? p K 45 12.6
  pp/dAu/AuAu 0 pp/AuAu
• ?(1530) ? ? p 100 21
  pp/dAu/AuAu 0
• ?(782) ? p p- p0 89 23 pp/dAu
  0
• ?(782) ? p0? 9 23
  pp/dAu/AuAu 0
• ?(782) ? p p- 2 23
• ?(782) ? ee- 7 10-2 23
  pp/dAu/AuAu in prog.
• F(1020) ? K K- 49 44
  pp/dAu/AuAu 0 pp/AuAu
• F(1020) ? ee- 3 10-2 44
  pp/dAu/AuAu in prog.

Life Time
f0, ? and a1 will be analyzed
3
Introduction f0 motivation
A. Badalà- SQM07- Levoca 24/06/-29/06/07
Nuclear Modification Ratios (RCP) for resonances
RHIC results have shown as, in the intermediate
pt region, nuclear modification factors depend on
the constituent quarks rather than on particle
mass.
Recent suggestion by Maiani et al. (Phys. Lett.
B645(2007)138) to use this observable to solve
the problem of the real quark composition of some
resonances as the fo(980)( or
?)
4
Introduction a1 motivation

• Volker Koch, workshop on dileptons at CBM, GSI,
  2007
• in the case of a full restoration of the symmetry
  the spectral functions of the ? meson and its
  chiral partner the a1 meson become degenerate.
• it has been proposed to measure the a1 mass
  spectrum in a hot and dense medium and compare it
  to the mass spectrum of the ? meson
• If the degeneracy would be observed it is
  expected to serve as an unambigious experimental
  signal for the detection of chiral symmetry
  restoration in the hot and dense medium.

5
Input info resonance parameters
PYTHIA mass 1.0 width 0.0 Br.rat.
decay products 0.520000 pi pi- 0.260000
pi0 pi0 0.110000 K K- 0.055000
K_L0 K_L0 0.055000 K_S0 K_S0
PDG
f0

• mass 980 MeV, width 70 MeV, KK-/pp- with
  BR0.11/0.52
• 
  mf lt 2mK988 MeV

a1
? mass 1260 MeV, width 400 MeV, p? with Br1
(enlarge statistics)
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Input info and assumptions

• Background SHAKER events
• dNch/dy const
• pt distribution p fit to Tevatron data, others
  mt scaling
• K?/p? 0.2, p?/p? 0.074, ?/p0 0.17
• Signal
• dNres /dy const, pt distribution mt scaling
• Ratios weakly depend on beam energy and event
  centrality
• 
  (dNres/dy)/ (dNch/dy)
• f0/ p- 0.07 (STAR data) ?
  0.0275
• ?/p 0.22 (STAR data) ? 0.0064
• a1/ p 0.013 (A.Andronic) ? 0.0051
• Cut pt gt 0.2 GeV/c, momentum resolusion sp/p 1
• No matter between a target and TOF/PHOS
  ? optimistic
  estimation of the signals

7
Input and assumptions - ratios
nucl-ex/0305034
nucl-ex/0403010
nucl-ex/0403026
nucl-ex/0510033
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Input and assumptions - spectra
nucl-ex/0510033
nucl-ex/0305034
mT scaling steeper than data
9
Geometrical acceptance
TOF ? - 900lt450
PHOS ? - 900lt100 ?? 1000
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pp signal and background
pp at LHC ? 106 SHAKER events with dNch/dy 5
f0 ? KK-
f0 ? p p -
like-sign or event-mixing techniques should be
used
11
pp signal and backgroud
? ? pp
a1 ? p?
like-sign or event-mixing techniques should be
used
12
pp S/B(?2s)
resonance m MeV ? MeV channel BR () dNres/dy dNch /dy accep () at pt0.5 S/B () S vSB
f0 980 70 KK- 11 0.0275 14 4092/19341 21.2 26.7
f0 980 70 pp - 52 0.0275 33 47121/1367900 3.4 39.6
? 1232 118 pp 100 0.0064 20 12546/171398 7.3 29.3
a1 1260 400 p? 100 0.0051 2 1001/286866 0.35 1.9
a1 150 1003/60616 1.7 4.2
a1 770 933/279455 0.33 1.8
even in pp, signal from a1 is very small (real
BR 1), S/B 10-3 !
13
pp S/B vs pt
for pt study higher statistics, 107, is needed
14
pp S/B vs pt
15
peripheral AuAu signal and backgroud
f0 ? KK-

• dNch/dy 2000 ?
• 0 - 5 centrality bin of AuAu
• dNch/dy 125 ? 60-65 centrality bin of
  AuAu
• 104 SHAKER events with dNch/dy 125

16
peripheral AuAu signal and backgroud
f0 ? p p -
? ? pp
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pp vs peripheral AuAu
dNch /dy statistics S/B () S /v(SB)
f0 ? KK- 5 106 4092/19341 21.2 26.7
125 104 1028/183053 0.56 2.4
f0 ? pp - 5 106 47121/1367900 3.4 39.6
125 104 11823/8562610 0.14 4.0
? ? pp 5 106 12546/171398 7.3 29.3
125 104 3150/1061100 0.3 3.1
S dNch /dy, if B (dNch/dy)2 ? S/B
(dNch/dy)-1, S/v(SB) does not depend on dNch/dy
to have S/v(SB) 10 105 events of a given
centrality bin are needed
18
AuAu other centralities
? ? pp
dNch /dy statistics S/B () S /v(SB)
5 106 12546/171398 7.3 29.3
125 104 3150/1061100 0.3 3.1
500 103 1292/1677720 0.077 1.0
2000 102 498/2676780 0.019 0.3
for ? it works! S/B (dNch/dy)-1
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A question to the STAR team

• f0 ? p p- 107 min.bias pp events
• 106 AuAu (40 - 80)
  events
• dNch/dy 125 - 20
• ? ? p p 6 106 min.bias pp events
• 2 106AuAu min.bias
• 2 106AuAu central
• 107 dAu min.bias
  dNch/dy 4 - 15
• No info on S/B, only spectra and ratios
• No a detailed paper, only short papers (SQM03,
  QM04, QM05)
• What are the S/B values?

20
Summary

• estimations of signals from the f0, ? and a1
  resonances with ALICE have been made
• pp S/B 10 for f0 and ?, 10-3 for a1
• AuAu S/B is smaller and follows S/B
  (dNch/dy)-1, S/v(SB) does not depends on dNch/dy
• like-sign or event-mixing techniques should be
  used to extract a signal
• to have S/v(SB) 10, 105 events of a given
  centrality are needed
• S/B increases as a function of pt
  107 events are needed
  for the pt study