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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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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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