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Dynamical Analysis of V-particles Decays. Podolanski-Armenteros Plot and its application for V0 particle search. Jaw-Luen Tang Department of Physics National Chung Cheng University Chiayi, Taiwan. Introduction. - PowerPoint PPT Presentation
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2004/8/20 1
J.-L Tang1
Dynamical Analysis of V-particles Decays
Jaw-Luen TangDepartment of Physics
National Chung Cheng UniversityChiayi, Taiwan
Podolanski-Armenteros Plot and its application for V0 particle search
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J.-L Tang2
Introduction• In 1953, Podolanski and Armenteros devised a method of an
alyzing the dynamics of two-body V decays to search for new unstable neutral particles in terms of measured quantities: p1, p2. (pp1+p2)
• The method based on constructing new variables: 1/P , Podolanski-Arementeros parameter pT the transverse momentum or=2pT/P, that related to the momentum components of each particles by conservation of momentum and energy which depend on the decay schemes.
• It is used to classify the V0-particles and is a convenient way of displaying ( identifying ) the decay schemes.
p1p2
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Armenteros analysis of V decay• Consider the decays of a neutral V0-particle of mass m and velocity
into two charged particles with mass m1 and m2 , m m1 + m2 + Q.
Center of Mass system Laboratory system
1 2
1 2 1 1 2 2
1 1 2 2 1 2
cos cos
sin sin sin /L L L
T
P p p
p p p p p
p p p p p P
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Armenteros Analysis• In the laboratory system, only p1,p2,and p can be measured, while th
e velocity of decaying particle is unknown. • Useful quantities : pT, independent of.
• In the -pT or planes, the points corresponding to a given decay scheme lie on an family of ellipses determined by the particle mass and the velocity the secondaries.
1 2
1 2
1 2
2 2sin sin
sinT
L L
L L
p
P
p p
p p
2 2
2 **
2 2
2 2 2
12 /
1( / ) ( / )
Tp
pp m
m P m P
* ( )
(2 / )Lp m
* *0
2 21 2
0 2
( ,cos )f p
m m
m
*2 *2 *2L Tp p p
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An Example: E896 H search
0sK
p
p
H p
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Another Example: HERA-B• HERA-B try to verify claims for
different exotic states, mainly they focus on: + (uudds) -> p K0
Armenteros plot
Λ
Ks
Λ
Λpπ
KSππ
Taken from A. Sbrizzi‘s talk
Ks
p+ +
-Decay chain
+(1540) -> p Ks
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Another example:Study of the K*(892)0 signal in pp ALICE events
Armenteros Plot
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0,4
-1 -0,5 0 0,5 1
alpha
qt
rho(770)
omega(782)
phi(1020)
k0s
Delta
Deltabar
Lambda
Lambdabar
K*(892)
Taken fromTaken fromGiuseppe’s talk.Giuseppe’s talk.
q(+)
q(-)
qt(-)
qt(+)
ql(+)
ql(-)
ql(+) - ql(-)
ql(+) + ql(-) =
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More example:Exotic Particle Searches with STAR at RHIC
Taken from Sonia Kabana’s talk
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LEPS: 10k + 10k events• Analyzed 10k + 10k MC events through current
TPCana0.43 tracking and vertex finder codes.
pK+p->p10k + 10k 10k 10k
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Cuts at invariant mass
Cut1 nvtx >1, ntrk>4, cdis<2mm, chi2prob<0.02
Cut 2Ks
Cut 6Cuts 1, out target
Vtxy>2mm-1650Vz<-1550
Cut4 Cuts 1, in target,
Vtxy<2mm-1650Vz<-1550
Cut7pT<0.2, ||<0.5
arm cut
Cut8pT>0.1, ||<1Ks arm cut
Cut9pT<0.2,>0.5arm cut
Cut10Cuts 1& 4& 7
Cut11Cuts 2 & 5 & 8
Ks
Cut12Cuts 3&6&9
Cut5Cuts 1, in target,
Vtxy<2mm-1650Vz<-1550
Cut 3
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Data Cuts at Armenteros diagram
Cut1nvtx >1
Cut 2 Cut 1 + ntrk>4
Cut 3Cuts 1+2 q1q2<0,
cdis<2mm, chi2prob<0.02
Cut 5Cuts 4 && in targetVtxy<2mm, Vz cut
Cut 6Cuts 4 && out target
Vtxy>2mm, Vz cut
Cut4Cuts 1+2+3
[ pt]<1
Cut7Cut 4 and arm cut
Cut8Cuts 4 and Ks arm cut
Cut9Cut 4 and arm cut
Cut10Cuts 5 and arm cut
Cut11Cuts 5 and Ks arm cut
Cut12Cuts 9 and arm cut
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Runs28641To28847
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