PRODUCTION OF ANTINUCLEI IN
pp COLLISIONS AT √s = 7 TeV
WITH ALICE AT THE LHC
Natasha Sharma
(for ALICE Collaboration)
Panjab University
Chandigarh, India
Natasha Sharma, ICPAQGP 2010
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OUTLINE
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Motivation
The ALICE Experiment
Particle Identification of (anti) nuclei
Background Rejection
Results – Raw yields of nuclei and anti-nuclei
Characteristic of events with particle mass
Summary and Outlook
Natasha Sharma, ICPAQGP 2010
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Motivation
i) Production mechanism of (Anti) Nuclei in a collision
ii) Thermal model predictions
iii) Model Comparisons
(Strangeness Canonical)
(Grand Canonical)
pp @ 7 TeV
THERMUS
Sciencexpress: March 2010
Paper in preparation..
See also A. Andronic, P. Braun-Munzinger,
J. Stachel and H. Stöcker arxiv: 1010.2995v1
Particle ratios with mass difference are very sensitive to temperature
 For AuAu @ 200 GeV data is in agreement with model
Natasha Sharma, ICPAQGP 2010
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Nuclei
Deuterons are hydrogen isotope: 1p + 1n: dud+udu
d
u
u
d
Anti-deuteron
 Contain 6 anti quarks
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6 anti-quarks move in one
direction to form an
anti-deuteron

u
d
 Tritons are hydrogen isotope: 1p + 2n: udu+dud+dud
 Helium-3 are helium isotope: 2p + 1n: udu+udu+dud
Natasha Sharma, ICPAQGP 2010
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The ALICE Experiment
ALICE TPC have pseudo-rapidity coverage more than -0.9 to 0.9 and azimuthal angle of 2π
Natasha Sharma, ICPAQGP 2010
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Particle Identification
(TPC)
pp @ 7 TeV
 Approximately 350 M events are analyzed
 Various nuclei are nicely identified in ALICE
Natasha Sharma, ICPAQGP 2010
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Event display
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d
d
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3He
Rigidity
Natasha Sharma, ICPAQGP 2010
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Background Rejection
Deuteron contains background from the material
DCAZ < 2.0 cm cut removes large fraction of background
Used similar cut for all other nuclei – t, 3He
Natasha Sharma, ICPAQGP 2010
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Deuterons: Raw Yields
(|y|<0.5 and DCAZ < 2.0 cm)
• d and anti-d are
identified via dE/dx
• Anti-d yield = Counts
from -0.2<DCAXY<0.2
• d yield = Counts – linear
BG from -0.2<DCAXY<0.2
Natasha Sharma, ICPAQGP 2010
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Anti-Deuterons: Raw spectra
Normalization and Efficiency correction yet to be done
Natasha Sharma, ICPAQGP 2010
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Tritons: Yields
(|y|<0.5 and DCAz< 2.0 cm)
Anti-t yield = Counts (from -0.05 <DCAXY<0.05)
t yield = Counts (from -0.05 <DCAXY<0.05) – BG (from
-0.3 <DCAXY<-0.1)
Natasha Sharma, ICPAQGP 2010
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Helium-3: Yields
(|y|<0.5 and DCAz < 2.0 cm)
Anti-3He yield = Counts (from -0.05 <DCAXY<0.05)
3He yield = Counts (from -0.05 <DCA <0.05) – BG from
XY
-0.3 <DCAXY<-0.1
Natasha Sharma, ICPAQGP 2010
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Event Characterization
Average number of tracks:
<ntr>pi+ ~ 13
 <ntr>p- ~ 15
<ntr>k+ ~ 15
<ntr>d+ ~ 17
<ntr>d- ~ 18
Performance
13.11.10
Average track multiplicity for events with deuterons and anti
deuterons is higher than others.
? Hint of particle production via coalescences
Natasha Sharma, ICPAQGP 2010
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Summary and Outlook
Summary • Raw yields for (anti) d, (anti) t, (anti) 3He are presented for pp
collisions at 7 TeV
• Significant number of (anti) deuterons have been obtained in pp
collisions
• Heavier anti-nuclei: anti-t and anti-3He are also observed
• Average track multiplicity for events with heavier particle is higher
Outlook o Get the final (corrected) yields of nuclei for pp collisions
o Search for (anti) hyper-tritons in pp collisions at 7 TeV
o Similar work will be done for PbPb collisions at √s=2.76 ATeV
Natasha Sharma, ICPAQGP 2010
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THANK YOU
Natasha Sharma, ICPAQGP 2010
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