Φ(1020) photoproduction in neutral decay channel
DESCRIPTION
Φ(1020) Photoproduction in Neutral Decay Channel. Heghine Seraydaryan. June 12, 2009. Outline. Theory Motivation Data and Selection of Events for p p K S K L p’ Preliminary Results Summary. . . , . p. p’. Φ(1020) Meson. Theory. Decay channels: - PowerPoint PPT PresentationTRANSCRIPT
Φ(1020) Photoproduction in Φ(1020) Photoproduction in Neutral Decay ChannelNeutral Decay Channel
Heghine Seraydaryan
June 12, 2009
Outline
Theory Motivation Data and Selection of Events for p p
KSKLp’ Preliminary Results Summary
Φ(1020) Meson. Theory
Decay channels:
K+ K- (49.2%)
KS KL (34%)
0,+ - 0 (15.3%)
(1.3%)
p p’
,
Production mechanisms:
Kinematics and observables:
Θ - helicity angleΦ - azimuthal angle
,cos)()(),,( 0WtfEftE
Motivation and Observations for the Charged Channel
Charged Channel
• The peak at about 2 GeV with width 0.2 GeV• Theoretical curves fail to describe the data
Note:
• The cross sections were obtained without cut on (1520)
Previous results for p pΦ(1020) p K+
K- :
• No photo-production data for Neutral Channel • We can check the cross-section behavior and slope behavior
Motivation
D.Tedeschi
Events cleaning for p Φ(1020) p KS KL p
Also cuts on momenta of the particles:
P + > 0.1 (GeV/c), P - > 0.1 (GeV/c)
Pp > 0.35 (GeV/c)
The particle identification was done by using DC and SC information
Three particle events were selected (p, +,-)
The invariant mass of (+,-) was taken to be mass of KS
Missing mass of
( p->p + -)X was taken to be mass of KL
Generator
The generator for meson was created using several iterations method
The generator is based on data.
Cross section is generated as:
As initial energy distribution the K+K- energy distribution was taken
(using Tedeschi results).
f(E) and ρ00 parameters were varied to make Monte Carlo fit the data.
The same thing was done for t distribution.
Gen GSIM RECSISGen, GSIM, RECSIS were used several times to obtain generator-data agreement.
α =3.4
Acceptances
Accep
tan
ce
t- tmin
E = 1.6 E = 1.65
E = 1.7 E = 1.75
E = 1.8 E = 1.85
E = 1.9
E = 2.0
E = 1.95
E = 2.05
E = 2.1 E = 2.15
E = 2.2 E = 2.25
E = 2.3 E = 2.35
E = 2.4 E = 2.45
E = 2.5 E = 2.55
E = 1.6
1.6 GeV E 1.65 GeV
Efficiency calculations for -
To obtain the efficiency for - ,two reactions were used:
(γp->p +) -
(γp->p - + +) -
Four momentum slices(0.1-0.15),(0.15-0.2),(0.2-0.3),(> 0.3)
180 θ bins360 φ bins (1 degree each)
missing - detected -
To obtain the efficiency for +, were used: (γp->p -) +
(γp->p - + -) +
and to obtain the efficiency for p ,were used: (γp-> + -)p (γp-> + - + -)p
missingdetected
efficiency
p = 0.125 GeV/c
p = 0.175 GeV/c
p 0.3 GeV/c
p = 0.25 GeV/c
Cuts and Corrections
We used:
Cuts
On momenta of the particles: P + > 0.1 (GeV/c), P - > 0.1 (GeV/c)
Pp > 0.35 (GeV/c)
To select K : |M(KS)-0.49765| < 0.008 (GeV/c2)
|M(KL)-0.49765| < 0.015 (GeV/c2)
To select : M(φ) = 1.02 ± 0.02 (GeV/c2)
To select background: M(φ) = 1/2*N(1.06 ± 0.02 (GeV/c2) )
Corrections • Standard g11 momentum corrections
• Standard g11 photon energy corrections
• Energy loss corrections for + , - and p
• Photon timing : 1 photon in 2 ns interval
• Acceptance corrections
• Efficiency corrections
Preliminary Results
For the φ cross section in the Neutral decay mode we observe a peak , which is shifted to 1.9 GeV and is slightly smaller, compared to the peak at about 2 GeV in the Charged channel.
We also observe some difference for the slope values of the two channels. For the Neutral channel they are much smaller in photon energy region (1.6:2.4) GeV.
The Neutral channel cross section is multiplied by branching ratio (1.447)
A. Thomas et al
CLAS PRELIMINARY
Preliminary Results : Angular Distribution Function
CLAS PRELIMINARY
CLAS PRELIMINARY
Helicity Frame
Preliminary Results : Angular Distribution Function
CLAS PRELIMINARYCLAS PRELIMINARY
Gottfried-Jackson Frame
The fit function had to be modified with an addition of a linear term cos, to be able to fit the data correctly.
+ C cos
Preliminary Results : Spin-Density Matrix Elements
CLAS PRELIMINARYCLAS PRELIMINARY
Helicity Frame GJ Frame
Preliminary Results : Angular Distribution Function
CLAS PRELIMINARY
GJ Frame
Summary
We analyzed φ(1020) production in Neutral decay channel from g11 data.
We measured the cross section, the slope and the angular dependences of the
cross section. We extracted spin-density matrix elements in GJ and Helicity frames.
ConclusionsThe slope of the φ production in Neutral channel is much smaller than
the Charged channel slope for the photon energy interval (1.6:2.4) GeV.
The cross section peak at 2 GeV in Charged decay mode is slightly larger than the one observed in Neutral decay mode.
Comparison of the W between the Neutral and Charged channels shows agreement for two energy bins in the Helicity frame. For the Charged Channel data is used T. Mibe’s measurements from Spring-8 .
The difference between the two channels must be investigated further.
1/
Efficiency calculations for +
To obtain the efficiency for + ,two reactions were used:
(γp->p -) +
(γp->p - + -) +
Four momentum slices(0.1-0.15),(0.15-0.2),(0.2-0.3),(>0.3)
180 θ bins360 φ bins(1 degree each)
The ratio of two is the efficiency
missing + detected +
Efficiency calculations for protons
To obtain the efficiency for p ,two reactions were used:
(γp-> + -)p(γp-> + - + -)p
Four momentum slices(0.1-0.15),(0.15-0.2),(0.2-0.3),(>0.3)
180 θ bins360 φ bins(1 degree each)
The ratio of two is the efficiency
missing P detected P
Large angle efficiency (1) comes from the events with two detectedprotons (are mostly background)
+ Data Corrections with Efficiencies
- Data Corrections with Efficiencies
Proton Data Corrections with Efficiencies
Acceptance Calculation
• events were generated in 4 (figure a)
• GSIM was used to simulate the detector
• RECSIS was used to reconstruct the
events as in the experiment (figure b)
• The acceptance was calculated as the
ratio of reconstructed simulated data,
presented on figure b, over the simulated
data, presented on figure a.
It was done for different energy regions
and different t bins.
a)
b)
c)A
ccep
tan
ceE
ven
tsE
ven
ts
t - t min
generated events
reconstructed events
generated
tedreconstruc
Generator and Data Agreement
E = 1.65
1.6 GeV E 1.7 GeV
E = 1.65 E = 1.75 E = 1.85
E = 1.95 E = 2.05 E = 2.15
E = 2.25 E = 2.35 E = 2.45
Data eventsGenerated events
Generator and Data Agreement
Data eventsGenerated events