study of d ++ resonance abundance in 158 agev pb + pb collisions at cern-sps
DESCRIPTION
Study of D ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS. Susumu SATO. Contents 1) Introduction ~ Relativistic heavy ion collision ~ 2) Thesis motivation ~ D measurement ~ 3) Experimental setup ~ WA98 at CERN-SPS ~ 4) Data analysis ~ corrections and errors ~ - PowerPoint PPT PresentationTRANSCRIPT
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Susumu SATO
Contents1) Introduction ~ Relativistic heavy ion collision ~2) Thesis motivation ~ measurement ~ 3) Experimental setup ~ WA98 at CERN-SPS ~4) Data analysis ~ corrections and errors ~5) Experimental Results ~ ,p spectra & yield ~6) Discussion ~ low mt enhancement of inclusive spectrum
~• Summary
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb
Collisions at CERN-SPS
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Picture of Relativistic Heavy Ion collisions
To understand fireball, need picture during “cooling with expansion”
[1: Before collision (~17 at SPS)]
- Lorentz contracted [2: During collision (~1fm/c)]
→stopping/heating
→hot/dense fireball [3: After collision]
→(thermal/chemical equilibrium) →”cooling with expansion” →thermal/chemical freeze out →hadrons(,K,p,…), e, …detection
Fireball
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
10-2
10-1
100
101
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
protonK+ ( x 1/1.5 )p+ ( x 1/35 )
mt-m(GeV)
Ed
dpmb GeV c
3
2 3/e je j
Ed
dp
mb
GeV c
3
3
2 3
FHG
IKJ
mt – m (GeV)
mt-scaling in proton – proton collisions
Single Particle Spectra (pp collisions)
s GeV23Nucl.Phys.B100(75)237
(1)Similar shape, and(2)Similar slope
for different particle species
(called mt-scaling)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
mt – m (GeV)
Single Particle Spectra (nucleus - nucleus collisions)
158 AGeV Pb PbNucl.Phys.A610(96)175c
(1)Different shape, and(2)Different slope
for different particle species
1
m
dN
dm
a u
t t
( . . )
Different shape and slope are observed.
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Two particle HBT correlation
Source size as a function of relative momentum
C p p R q
q q q q q
q p p
p p p p p i
inv
inv x y z
i x y z
2 1 22 2
2 2 20
2
1 2
0
1
1 2
( , ) exp
,
( , , , ) ,
e j
quantum interference to measure source size (R)
R
C2: detection probability of two particles at the momentum of p1 and p2
(R=6fm,=1)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Two particle HBT correlationin nucleus nucleus collisions
Source size as a function also of average momentum
C p p
R q f R q q
q q q q p p
K p p p p
z z
x y
x x y y
2 1 2
2 20 0
2 21 2
1 22
1 22
1
1
2
( , )
exp ; ,
,
b gd i
b g d i
Beam Direction (z)
TransverseD
irection (x,y)
p1p2
KT
q
q
Eur.Phys.J. C2(98)661
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Expanding Fireball Model (1)
mass dependence of mt spectra slope
p
-
p -
+
K+ K -
Naively, Expansion Fireball is applicable !
NPA610(96)175
→linear mass dependence ↓ parameterized naively T = Tf +mass ・〈 f 〉 2
Mass(GeV/c2)
Slo
pe(G
eV)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Expanding Fireball Model (2)~ example of good parameterization ~
Good explanation both for singles and two particle correlation,
but not using lower mt-region
(1) Single spectra: transverse kinetic energy (mt) spectra
PRL80(98)3467→parameterization for
different particle species Tf ~139MeV, 〈 f 〉 ~0.42c (2) Two particle HBT correlation
Habilitation(’97/T.Peitzmann)
→Boost invariance for expansion 〈 f 〉 =R/f ~ 0.430.16c
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Thesis Motivations
(1) Measurement of particle production of a new particle species;
→(1232) in 158 A GeV Pb + Pb central collisions.
(2) As a basic problem to understand both single particle spectra and HBT correlation, low mt pion enhancement is observed.
→By using the result of explicit measurement of resonance, the contribution of to low mt enhancement is acquired, then aiming to get footing of the validity of the expanding fireball model.
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Authors Contributions
Design of experimental detector ● Time-of-Flight (TOF) detector ● Optimal alignment of chambers in magnetic spectrometer
Construction, test, installation, and operation of detectors ● TOF detector ● Streamer tube tracking (STD) detector ● Start counter
Programming of control and reconstruction software ● HV control for TOF ● Online monitoring for TOF, STD
● Momentum reconstruction
Physics Analysis ● Pion and proton single spectrum ● Yield of (1232) resonance
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Δ++ resonance● Lowest resonance of nucleon
● M ~ 1232MeV (in Breit-Wigner function )● c ~ 1.8 fm; (~111MeV)
● Isospin3/2, Spin 3/2
● Decay into pion and proton with >99% branching ratio 99% p
cf
n
p
n
p
n
.
~
~
~
~
R
S
||||
T
||||
50%
50% 0
99%
0 50%
50% 0
e j
e j● Decayed pion gives lower transverse kinetic energy
y
Pt(mt)(GeV/c)
0-1 10
0.4
0.8 ++
p
+
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
PAD Cham.
Beam( 208Pb:158AGeV)
Magnet
Start
TOF (Stop counter)
Streamer Tube Det.
LEDA(EM.Cal.)
+P.ball, SPMD
PMD
ZDC(Had.Cal.)
MIRAC(Had.Cal.)
21.5m
Target (208Pb: 0.239mg/cm2)
Characterize Fireball from various aspects• [Hadron] momentum + PID; w/Mag. Spectr.• [Photon] E w/EM.Cal. • [Hadron] global ET, E0; w/Had.Cal.• [Photon] mult. distr.; w/PMD • [Charged particle] mult. distr.; w/SPMD, P.ball
WA98 experimental setup
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Magnetic spectrometer is in good operation
~ 1% at 2GeV/c
0 1 2 3 4 5 0
1%
σ p /
p
2%
0.5%
1.5%
-0.4 0 0.4
10k
5k
N start~30ps
Detector resolutions (p, Tstart, Ttof)
p(GeV/c)
Tdif (ns)
Ttof (ns)
N800
400
0 0.8-0.8
~85ps tof
~1.3mm, //~2.1mm (PAD1)~2.6mm,// ~7.0mm(STD1)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
0
• Clear Particle Identification by ToF method
FH IK
RSTUVWp
TOF c
L2
21
~0.02 (GeV/c2)2 at 2GeV/c for π
0.00
0.10
0 2
0.05
41 3
m2(GeV2/c4)
p(GeV/c)
2
4
6
8
0 0.5 1 1.5
p(G
eV/c
)
pK +
Particle Identification
σm
2
(GeV
/c2 )
2
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Ed N
dpE
d
dp
Ed N
dpE
d N
m dm dy d
d N
m dm dy
trig
t t
t t
3
3
3
3
3
3
3
2
1
2
Parameterization [1]for , p single particle spectra
Kinematical parameters
yp m p
p m p
z
z
1
2
2 2
2 2ln
m m p p m mt x y 2 2 2
Transverse kinetic energy
(longitudinal) rapidity
y : Lorentz invariant
Lorentz invariant differential yield
if symmetry
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Measure around mid-rapidity, where hot fireball is expected the most.
(←ytarget =0) ycm=2.9 ( ybeam=5.8 →) y
Geometrical Acceptance
Fireball
mt-
m(G
eV)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Data selection
• Event selection Single beam (3 in ADCstart) FEE linear region (5.7% in Tdynamic) not after-chamber-spark (0.8sec) event
ADCstart 1 [ch]
AD
Cst
art 2
[ch]
•Track selection image on target (3 in B// direction) image on TOF2 (2.5on 2-D plane)
•PID selection m2 (2.5 in the p)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Geometrical acceptance and Efficiency correction
Averaged eff. PAD1 83% PAD2 80% STD1 91%STD2 97%
geo t cham cham cham decaycham
m y X Y L p, ( , ) ( / ). . ..
a f
p
PAD1
STD2STD1
PAD2
By the Monte Carlo Simulation (GEANT3.15)
cXmt
gyY
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
100
101
102
103
0 0.2 0.4 0.6 0.8 1
d2N
mt-m (GeV)
mt
dmt
dy1
158 A GeV Pb + Pb central(GeV-2)
● + (WA98)
○ + (NA44)
◆ proton(WA98)
◇ proton(NA44)
Single spectra
Slope(MeV)
WA
98
NA
44(*)
π+142
±3
156
±3
p251
±25289±7
mark in plot
filled open
(*) Nucl.Phys.610(96)175
mt-m(GeV)
Consistent shapes with other experiments
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Parameterization [2] for yield by invariant mass method
m E E p pinv p p e j e j2 2
Yield m
Yield m
Yield m
raw inv
inv
comb B G inv
a fa fa f
. . .
Invariant mass
Invariant mass distribution
should be evaluatedYield mcomb B G inv. . .a fInvariant mass (GeV)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Mixed Event technique
Combinatorial background is assumed to be proportional to mixed events
Yield m Yield mcomb B G inv
assume
mixed inv. . .a f a f
Mixed events: p and + from different events paired in 100 every events
EVENT 1p
p
p
EVENT 2p
p
p
example
Invariant mass (GeV)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Two normalization methods
Two methods should be consistent
q:relative momentum of the pair in its C.M. frame,:180MeV/c
Yiled mq
q m minv
assume
inv
LNM OQP
a fe j
3
3 3 21
4 1 /
(1) Tail method
normalize only in higher minv region
(2) Breit-Wigner + Background method
normalize in any minv region,assuming Yield++ follows Relativistic Breit-Wigner
(PRL79(’97)4354) Invariant Mass (GeV)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Clear yield can be extracted by tail method
Tail method
=0.0860.014
(GeV)
E0=1.2370.006
Invariant mass (GeV)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Breit-Wigner + Background method
Again, clear yield can be extracted by B.W.+BG. method
Invariant mass (GeV)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
(3)Local multiplicity (N) on TOF
Systematic error of N/ ev. on extraction method
Less dependence on extraction parameters
(2) Tail method: 0.021
(1) Breit-Wigner + B.G. method: 0.022
N
/ ev.
Mth. (GeV)
1.4 1.5 1.6 1.7 1.4 1.5 1.6 1.7 1.4 1.50
0.05
0.10
0.022 0.022 0.018N=2 N=3 N=4
Nev . Poisson
<N>=2.6
0
1k
2k
N2 4 60
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
N N Nraw mix For ,
F
HGG
I
KJJ
FH IK
e ja fa f e j a f
a f e i
2
2
2
2
2
N
N
N N N
NN
whereN N
N
raw
mix
raw mix
mixmix ii
raw
mix
~
~
,
~
,
Statistical Error
Major contribution of error is large Combinatorial Back Ground
Error propagation gives
( 50.0% )
( 49.9% )
( < 0.1% )
~ 45% N
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Isospin consideration
Factor from Np/N++ to Nnucleon/N is 2.0.
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Yield summary table
At SPS, delta yield is, for the first time, directly measured
Value and Statistical Error
++ / spectrometer /ev. (raw) 0.022 0.010
proton / spectrometer/ev. (raw) 1.080 0.010
++/proton (raw) 0.021 0.009
trk (3or4cham.) 0.79 0.02
PID 0.60 0.02
geo 0.145 0.005
++/proton ( trk , PID, geo corrected) 0.31 0.14
/nucleon (isospin corrected)
0.62 0.28 (stat.) (45%)
Systematic Error
Uncertainty of Tracking efficiency 0.06 (sys.) (10%)
Difference in normalization method 0.02 (sys.) ( 4%)
Difference for different local multiplicity 0.08 (sys.) (13%)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Higher population is seen at SPS
PLB477 (2000) 37-44 Δ
(123
2)
nuc
leon
(%) 100
80
60
40
20
0 1 10 100Ebeam(AGeV)
Population ratio: Δ/ nucleon
Acquired from / p,Isospin correction done for
82208Pb
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
100
101
102
103
0 0.2 0.4 0.6 0.8 1
Low mt enhancement is seen in local mt slope (Next)
mt – m (GeV)
0 0.4 0.60.2
102
10
1
2
2
2
m
d N
d y d m
GeV
t t
( )
+
Neighboringseveral points for
local mt slope
1
Low mt enhancement in Pb + Pb (1)
103
0.8 1
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
0.05
0.1
0.15
0.2
0 0.2 0.4 0.6 0.8 1
The mt enhancement is seen in + spectrum in Pb + Pb collisions
Center of fitting region in mt – m (GeV)
Loc
al s
lope
(G
eV)
Low mt enhancement in Pb + Pb (2)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
pp collision is described well in mt exponential
1
10
100
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7mt-m
0(GeV)
Ed
dpmb GeV c
3
32 3
/e je jFitting Liney=a*exp(-x/b)
a=82.48 (er. 3.71)b=0.1532 (er. 0.0026)
chi square / n.d.f = 8.83 / 6
mt – m (GeV)
pp collisions
100
10
1
Ed
dp
3
3
mb GeV c/ /2 3e j
0 0.4 0.60.2
Fitting Liney=aexp(-x/b)a=82.5±3.7b=0.153±0.0032/n.d.f=8.8/6
s GeV23
Nucl.Phys.B100(’75)237
+ at mid-rapidity
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Candidates of low mt enhancement
There are more than one candidates
(1) Collective motion
(2) Coulomb effect
(3) Resonance decay
+
++
e.g. Collective radial expansion
Repulsion/Attraction from Charges
+ decay gives lower mt by kinematics
y
Pt(mt)(GeV/c)
0-1 10
0.4
0.8 ++
p
+
p
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Collective motion (Thermal+expansion)
spectra shape is little affected by Collective motion
MeV〈〉 =0.42c
Describing well for different particle species
except low mt , and shape of is little
affected by collective motion
PRL80(’98)3467
consistent also with two particle HBT correlationDashed line:
exponential for eye guide
1
m
dN
d m
a ut t
( . . )
mt – m (GeV)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
101
102
103
0 0.1 0.2 0.3 0.4 0.5 0.6mt-m (GeV)
d2N m
tdm
tdy
1(GeV-2)
◆ + ◆ -
---exponential
RatioN
N
0 0.40.20
1.0
2.0w/Coulomb
No Coulomb
Low mt Enhance
1
2
22
m
d N
d y d mGeV
t t ( )
Low mt enhancement is seen in both charge, and Coulomb effect appears as difference between + and –.
Coulomb effect
Coulomb
mt – m (GeV)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
10-1
100
101
102
103
0 0.2 0.4 0.6 0.8 1
d2Nmt
dmt
dy1 (a.u.)
mt-m (GeV)
Δdecay +Thermal Expansion
●
■
(---- Thermal expansion component)
――
π + WA98)(
π + NA44)(
――
( Upper and lower error )
N
Np Sc Not Sc
NotSc p NotSc
( .) ( . .)
( .) ( .)
Contribution of Δ Resonance
“thermal source” + “Δ resonance decay” isconsistent with the low-mt enhancement of π + .
Δ( invariant mass) with a factor (1+α)
→consistent with simulation
thermal modelT=139 MeV,〈〉 =0.42c
+
included evaluation
mt – m (GeV)
1 2
m
d N
d y d mt t
(a.u.)
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
Conclusion(1) For the systematic study of hadron production in 158 A GeV
Pb + Pb collision, magnetic spectrometer with good PID capability is constructed.
(2) At 158 A GeV Pb + Pb collisions, + and p inclusive single mt spectra are measured. Inverse slopes are 142 3 MeV (fitting region: mt – m > 0.2 GeV) for + and 251 25 MeV for proton. In the pion spectrum, clear low mt enhancement is observed.
(3) 158 AGeV Pb + Pb collisions, resonance yield is, for the first time, measured directly. The /nucleon ratio is
0.62 0.28 (stat.) 0.16 (sys.).
(4) Spectrum shape with consideration of decay on thermal expanding fireball follows low-mt enhancement of π + . The additional factor is consistent with a cascade simulation that gives contribution of decay with re-scattered proton.
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CERN-SPS-WA98 Susumu SATO
Study of ++ Resonance Abundance in 158 AGeV Pb + Pb Collisions at CERN-SPS
At SPS, is not measured, while AGS tells its importance
At AGS, good description with decay
in RQMD
PLB351(95)93
at AGS (not directly measured) andMeasured PID at SPS