Upload
afya
View
71
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Cross section e + e - -> wp 0 -> p 0 p + p - p 0. Antonio De Santis Simona Giovannella. w. w. r,r ’. f. p 0. p 0. Amplitude: how to measure BR( f->wp 0 ). f contribution in cross section could be represented as interference with continuum process r->wp. - PowerPoint PPT Presentation
Citation preview
A.De Santis Radiative Meeting 28/04/06
Cross section ee
Antonio De Santis
Simona Giovannella
A.De Santis - Radiative Meeting 28/04/06 2
Amplitude: how to measure BR()
2
0 1
D
mZEE
EPD
mA
D
m
f
g
EE f
2
'
2'
22
3
2
0
4
’
mEBE m 100
contribution in cross section could be represented as interference with continuum process Interference is parametrized by term (Z) at -resonace peak.
A.De Santis - Radiative Meeting 28/04/06 3
Amplitude: MC generatorAll term which differs for exchange between two 0’s or different charge must be summed. Resulting matrix element (M) could be expressed as modulus squared of current composed by two term(0’s permutation) each composed by tree terms ( charge)
20020M
J
(p2)
(p4)
(p1)
(p3)
)(),,,(),,,(),,,( 3241323412314200
0 pppppptpppptpppptGJ
)()()()(
)()(
)(),,,(
31441324133142214334
431
12
4321
ppppppppppppppp
ppDpPD
pPFppppt
Reference: hep-ex/9904024 v2
A.De Santis - Radiative Meeting 28/04/06 4
Analisys strategy
• Acceptance– One vertex at Interaction Point (IP)– Two tracks connected at vertex– Four neutral cluster with:
• Eclu grater than 10 MeV
• ToF compatible with prompt • |cos()| < 0.93
• Kinematic Fit• Fine selection:
– 2 < 50
– m/m
• Slice dataset in function of ECM
• Signal events counting (fit via HMCMLL) • Cross section fit
A.De Santis - Radiative Meeting 28/04/06 5
Data vs MC: 0 recoil mass
)(0 MeVM recoil
)(0 MeVM recoil
old MC
new test MC
)(0 MeVM recoil
Left side: data(2001+2002) fitted with old self-made MC production.Right side: data(2002) compared with new MC test production (100pb-1 all_phys LSF 0.2)
A.De Santis - Radiative Meeting 28/04/06 6
Data vs MC: cos()
][)cos( 0 inclusive
][)cos( 0 inclusive
][)cos( 0 inclusive
old MC
new test MC
Left side: data(2001+2002) fitted with old self-made MC production.Right side: data(2002) compared with new MC test production (100pb-1 all_phys LSF 0.2)
A.De Santis - Radiative Meeting 28/04/06 7
Data vs MC: cos(±)
)cos( )cos(
old MC
new test MC
Left side: data(2001+2002) fitted with old self-made MC production.Right side: data(2002) compared with new MC test production (100pb-1 all_phys LSF 0.2)
A.De Santis - Radiative Meeting 28/04/06 8
Data vs MC: M()old M
C
new test MC
Left side: data(2001+2002) fitted with old self-made MC production.Right side: data(2002) compared with new MC test production (100pb-1 all_phys LSF 0.2)
)()( MeVM )()( MeVM
A.De Santis - Radiative Meeting 28/04/06 9
Analysis Efficiency (MC)
ToTFineAcc 0.472 ± 0.005 0.894 ± 0.003 0.422 ± 0.006
A.De Santis - Radiative Meeting 28/04/06 10
Systematic errors: counting contribution
Source Weight (10-2)
L 0.5
Trg 0.4
Clu 0.7
Acc 0.3
ToT 1.0
Prelim
inar
y
Possible source of systematic error in counting:• Luminosity factor;• Trigger efficiency;• Clustering efficiency;• Resolution effect on acceptance cut.
All these effects are summed with counting fit error.
A.De Santis - Radiative Meeting 28/04/06 11
Cross section fit
Preliminary
0073.00948.0)(
011.0103.0)(
11.068.80
Z
Z
mFit result:
Radiative correction for the cross section are calculated through convolution with radiator function at fit level.
2
0 11
D
mZmEBE m
tot
count
L
N
intexp
A.De Santis - Radiative Meeting 28/04/06 12
Systematic errors: impact of fine cut and counting variable
sysstat
sysstat
sysstatm
Z
Z
006.0008.0095.0)(
004.0011.0103.0)(
08.011.068.80
Systematic errors are evaluated as r.m.s. of fit-parameter distribution
obtained varying value for angular coefficient B in cross section function
and varying counting-fit distribution.
A.De Santis - Radiative Meeting 28/04/06 13
• SPARE
A.De Santis - Radiative Meeting 28/04/06 14
Amplitude current term
Form factor
Inverse propagator
)()(
)()(
)()(
)(),,,(
3144132
4133142214334
431
12
4321
pppppp
ppppppppp
ppDpPD
pPFppppt