Kaon and Pion kinks study

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Particle identification _at_ALICE Separation/Identifi
cation of kaons/pions in pp interactions at ALICE
Experiment based on the kinematics of their decay
Physics Department University of Athens
EESFYE , 28/3/2007
M.Spyropoulou-Stassinaki
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• Introduction
• Status of ALICE setup
• Particle Identification ( PID) in ALICE
• K/p decay to muon neutrino kinematical
  properties and kaon identification in Pb-Pb and
  pp interactions

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The ALICE Detector at CERN LHC A Large Ion
Collider Experiment

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MARCH 2007 Closing of Machine on August 31,
2007 Run pp Inter. At 0.9 TeV CM Energy


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March 15, 2007


M. Spyropoulou-Stassinaki
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ATHENS_at_ALICE (Athens-Phys.Dep.)Quark-Gluon-Plasm
a (7 TeV/nucleon)
Staff memb.
Post-Doc.
Graduate St.
A. PETRIDIS ?. STASSINAKI E.TSILIS M.VASSILIOU
A.BELOGIANNI P.GANOTI S.POTIRAKIS
P.CHRISTAKOGLOU G.GEORGOPOULOS F.ROUKOUTAKIS
M.FRAKGIADAKIS G. TAGRIDIS 10 Phys.
Students S.TATSIS (Techn.)
Contribution to QGP Study 1.Charge
Flactuations/Balance function 2.Flactuations of
Particle density 3. Strange Particle Production
(?, ?(1520)....) 4. Quarkonium Production(J/?,?)
Contribution to Detectors develop. 1.Design,
development construction of H.V. distribution
system for the TRD 2.Integration of the ALICE
DAQ system and monitoring development for the
ALICE Forward detectors (?0,V0,FMD) 3.Design and
development of the Control System (DCS) for the
TRD 4.Design-development of a
monitoring System for the Gate Pulser of the TPC

5.Software development for PID in cent ALICE
detectors(TPC,ITS,TRD) 6.Development of a
kinematic method for Particle Identification(PID)
in ALICE experiment
M. Spyropoulou-Stassinaki
EESFYE , 28/3/2007 ( IOANNINA 2006)
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ALICE Experimental Setup is a very good tracker.
Most of the QGP signatures require Particle
IDentification (PID). For example strange quark
production in hot QCD is far from being
understood in Pt gt 5 GeV/c. Experimental
cross-checks requiring high statistics and
precision in a large Pt range are needed to
fully explore the properties of dense matter.

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full bars3s separation, dashed bars2s
separation
PID in ALICE
ALICE PPR CERN/LHCC 2003-049
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Kaon is the lightest strange hadron, with a high
branching ratio to muonic decay channel ( 63,26)
and large Geometrical acceptance in the central
barrel of ALICE (TPC). This decay can be measured
as a kink. The reconstruction of the kink
topology ( secondary vertex with mother and
daughter tracks of the same sign) is a Key
technique for identifying kaons over momentum
range wider than that achieved by combining PID
signals from different detectors. Background of
kinks in kaon study are the kinks from pion
decay. The kink topology is important in both
Pb-Pb collisions and pp interactions (which will
be used for comparison with the Heavy Ion
interactions). The pp data will be the first
sample which will be collected In the first
running period in autumn of 2007.

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M.Spyropoulou-Stassinaki
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Kaon and Pion decays
kinks
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Branching ratios taken into account
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The momentum of the daughter muon in the K/p
rest frame is 236 and 30 MeV/c respectively.
This is the maximum Qt value of the muon in the
Lab frame.
The decay angle in the parent rest frame and in
the Lab system are connected as
M.Spyropoulou-Stassinaki
EESFYE , 28/3/2007
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M.Spyropoulou-Stassinaki
EESFYE , 28/3/2007
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The Athens group has published an ALICE
Internal Note on K/p separation for Pb-Pb
interactions at 5.5 TeV, based on the kinematics
of their decays into muon neutrino
(ALICE-INT-2006-012 , 8/2006) and a contribution
to ALICE PPR Vol II, CERN/LHCC 2005-030,
5/12/2005 Plots providing information for K/p
separation ( like Qt, decay angle) will be
presented. The expected yields of kaons
identified through kink study have been
calculated.
M.Spyropoulou-Stassinaki
EESFYE , 28/3/2007
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Muon Qt for the decays ? ? µ?µ and p ?
µ?µ
M.Spyropoulou-Stassinaki
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The next two dimensional plot is shown
momentum versus lab decay angle between daughter
and mother tracks for Kaon and Pion to muon
decays, together with the theoretical curves for
the maximum Lab decay angle
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Kaon/pion decay to muon neutrino
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An estimation of K/p yields from kink decays in
one year of running of Pb-Pb in ALICE is
required in a higher momentum region, especially
above 4 GeV where the K/p identification is poor
from the ALICE detectors and the region is
important for the dense matter study.2000 HIJING
events have been used in the simulation. For
such a study the number of expected yield is
given by N(observed) N(generated) x Geom.Acc x
Rec. Eff. So, the spectra (e.g. ?, Pt ) for
generated particles are needed, as well as well
as the calculation of Geometrical Acceptance and
Reconstruction efficiency

EESFYE , 28/3/2007
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Kaon yields from K-gtµ? decay, in one year of
running Pb-Pb int. Reliable statistics up to pT
13 GeV/c
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In the present study we have used generated
events from the pre-PDC06 production (pp
interaction at 14TeV) The plots expected to
provide information for K/p separation like Qt
of daughtrer track, decay angle of kink tracks
will be presented
M.Spyropoulou-Stassinaki
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The analysis in most plots is restricted in -.9lt
? lt .9 and radius of the kink vertex inside the
Central TPC volume with radius 110 cmlt Rlt250cm
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20k pp events at 1.4 TeV
1.181.301 Generated Pions, 10p/ev. in ?lt0.9
entries
149.861 Generated Kaons, 0.95K/ev. in ?lt0.9
entries
Pseudorapidity, ?
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Kink topology study, pp int., 60k events
All kinks from primaries, 32164 tracks
Ntrack
K -gt µ ? , 2934 tracks ?lt0.9, 110ltRlt250cm

Ntrack
Qt,GeV/c
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Red kaons to µ ? Blue pions to µ?
Lab.Decay Angle, Degrees
Mother mom., GeV
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K-gtp... Rec. ESD
K-gtµ? Reconstr. ESD
tracks
Lab.Dec. Angle, Degrees
2934 K
1339 K
Mother mom., GeV
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These two plots show that with simple selection
on Qt and the kink decay angle at a given
mother momentum, a good Kaon/pion separation is
possible in a wide range of Pt.
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K to µ ?, ?lt0.9, 120ltRlt220 cm
GeV/c
Degr
R, cm
Mother momentum, GeV/c
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Kaons decaying to µ ? , 60k pp events
K-gtµ? gen., ?lt0.9
entries

Kaon gen. ? lt0.9
entries
K-gtµ? gen., ?lt0.9, 1.1ltRlt2.5 m
K-gtµ?, REC. ?lt0.9, 1.1ltRlt2.5m


Geom. Acc.

Rec. Eff.
Pt, GeV/c
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60k pp ev., yields of kaons from kinks to muon
Gen.sample

No of kaons


G.Acc. Rec.Ef.

yields
No of kaons
Pt , GeV/c
M. Spyropoulou-Stassinaki
EESFYE , 28/3/2007
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Some statistics from kinks, 60k pp events at 14
TeV
? lt 0.9 , 1.1 m lt radius lt 2.5m (
central TPC ) All kinks
41286 All kinks from primaries
32164 Fake kinks from prim. p to
µ?, REC., rest. etaR 11190 K gen.
inside restricted eta 65684 K to µ?,
gen, restr?cted eta 18480 K to µ ?,
gen, restr. Eta R 5319 K to µ ? ,
REC. rest. EtaR 2934 K to p ... ,
REC rest. Eta R 1339



M. Spyropoulou-Stassinaki
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Summary and future plans The K/p separation is
possible by using the kinematical properties of
their decay to muon neutrino. The kink study is
promising for K/p PID in a wide Pt range. This
result is an important complementary PID method
for a variety of Physics topics, like resonance
studies, K/p ratios, single particle spectra..
The new simulated pp data ( 106 events) will
be analyzed in the next two months. We plan to
investigate the effect of K-identification from
kinks in resonance signal extraction. The first
estimation gives an increase of the signal by at
least 15.

M.Spyropoulou-Stassinaki
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Kink mom. of mother trcak VRS thetalab bet.
Mother-daughter
p? µ ?
?trac
Same tracks
K ? µ ?
? ? p..
Mother momentum, GeV
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Multiplicity Measurements
5 measurements can give us the multiplicity
TPC ? n tracks
ALICE ç coverage

• ITS Pixel
• n clusters (in layer 1)
• n tracklets

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Kaon, Pion identification based on the different
kinematics of their decays to muonneutrino The
kinks will provide a complementary method for K/p
PID in a wide momentum range. Variables like
the Lab decay angle at a given momentum of the
mother particle K or p and the Qt of the produced
daughter muon may be used for K/p separation.
M.Spyropoulou-Stassinaki
EESFYE , 1/4/2007
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M.Spyropoulou-Stassinaki
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Kaons decaying to µ ?, 20k ev
Kaon gen. ? lt0.9
K-gtµ? gen., ?lt0.9
entries
K-gtµ? gen., ?lt0.9, 1.2ltRlt2.2
K-gtµ?, REC. ?lt0.9, 1.2ltRlt2.2m
Rec. Eff.
Geom. Acc.
pT, GeV/c
M.Spyropoulou-Stassinaki
EESFYE , 1/4/2007
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60k pp ev., yields of kaons from kinks to muon
Gen.sample
No of kaons
G.Acc. Rec.Ef.


yields
No of kaons
Pt , GeV/c
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Kaons decaying to µ ? , 60k pp events
K-gtµ? gen., ?lt0.9

Kaon gen. ? lt0.9
entries
K-gtµ?, REC. ?lt0.9, 1.2ltRlt2.2m

K-gtµ? gen., ?lt0.9, 1.2ltRlt2.2

Rec. Eff.
Geom. Acc.
pT, GeV/c
M. Spyropoulou-Stassinaki
EESFYE , 1/4/2007
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