Measurement of R with KLOE-2
description
Transcript of Measurement of R with KLOE-2
Measurement of R with KLOE-2
G.V. & F.N.13/1/2010
Error budget on aHLO
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~40%
~75%(mostly 2)
~55%
contributionserror2
Very important also the region 1-2 GeV !!!
€
e+e− → π +π −
in the range < 1 GeVcontributes to 70% !
But
aHLO=5.3=3.3(s<1GeV) 3.9(1< s<2GeV)) 1.2(s>2GeV)
aexp - a
theo,SM = (27.7 8.4)10-10 (3.3)8.4 = ~5HLO~3LbL6BNL
1.6 NEW G-23 4 3
aHLO=5.3=3.3(s<1GeV) 3.9(1< s<2GeV) 1.2(s>2GeV)
aHLO 3=2.5 (s<1GeV) 1.5 (s<1GeV) 1.2(s>2GeV
This means: HAD ~ 0.4% s<1GeV (instead of 0.7% as now)HAD ~ 2% 1<s<2GeV (instead of 6% as now)
7-8if 27.7 will remain the same)
A rough estimate for g-2
FJ08
[Eidelman, TAU08]
Precise measurement of HAD at low energies very important also for em !!!
Comparison of error profiles for em(MZ) and a
Direct integration of energy points for a
Use of Adler function (It allows to use pQCD in a safer way down to 2.5 GeV) for em(MZ)
Extremely important region since its accounts for:-80% of the total error on
had (using Adler function)- 95% of the tot error on a
R at 1% in the region s < 10 GeV improvement of ~3 in (MZ)
1% in the region 1<s < 2.5 GeV (which is known with 6% accuracy) improvement of ~5 on (MZ) as evaluated “today” by direct integration
Direct integration of energy points for em(MZ)
region 2m<s < 2
e+e- data: current and future/activities
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KLOE-2(?)
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~7-15% ~6%
KEDR(3-5%, 15%)
Impact of KLOE-2 on inclusive measurement
s (GeV)s (GeV)
1) Most recent inclusive
measurements: MEA and B antiB,
with total integrated luminosity of
200 nb-1 (one hour of data taking at
1032 cm-2 sec-1).10% stat.+ 15%
syst. Errors
2) With 20 pb-1 per energy point (1year
of data taking at 1032 cm-2 sec-1 ) a
precise comparison exclusive vs.
inclusive can be carried out
s (GeV)s (GeV)
L int
(nb-1
)
o MEA, 14 points, MEA, 14 points, Lett. Nuovo Cim.30 (1981) 65Lett. Nuovo Cim.30 (1981) 65
• B antiB, 19 points, B antiB, 19 points, Phys.Lett.B91 (1980) 155Phys.Lett.B91 (1980) 155
20 pb20 pb-1-1
Not easy task
Statistics OK @ 1032cm-2 sec-1 (scan)
Systematics most likely under control, given the excellent performances of KLOE+inner tracker
Precise determination of beam energy would help (using BS Compton)
Exclusive vs inclusive?
Can KLOE-2 measure R with 1% error in the region 1-2 GeV?
Impact of DAFNE-2 on the range [1-2] GeV (2)st
atis
tical
stat
istic
al
had
had
h
adhad
s (GeV)s (GeV)
BaBar, with the published BaBar, with the published LLintint per point per point
BaBar, with 10 BaBar, with 10 (the present (the present LLint int ))
DAFNE-2, with 20 pbDAFNE-2, with 20 pb-1-1 per point per point
comparison among the present BaBar analysis, an (O(1 ab-1)) BaBar update,and Lint = 20 pb-1 per energy point @ DAFNE-2, in the impact on hadhad:
: O(2%) | O(0.7%) | O(0.5%)
Babar systematic error:5% on 2
(8-14% for 2
Stat error
Impact of DAFNE-2 on the range [1-2] GeV (2K2)st
atis
tical
stat
istic
al
had
had
h
adhad
s (GeV)s (GeV)
comparison among the present BaBar analysis, an (O(1 ab-1)) BaBar update, and Lint = 20 pb-1 per energy point @ DAFNE-2, in the impacton hadhad :
: O(15%) | O(5%) | O(3%)
BaBar, with the published BaBar, with the published LLintint per point per point
BaBar, with 10 BaBar, with 10 (the present (the present LLint int ))
DAFNE-2, with 20 pbDAFNE-2, with 20 pb-1-1 per point per point
Babar systematic error: 10%
Stat error
Impact of DAFNE-2 on the range [1-2] GeV (3)st
atis
tical
stat
istic
al
had
had
h
adhad
s (GeV)s (GeV)
BaBar, with the published BaBar, with the published LLintint per point per point
BaBar, with 10 BaBar, with 10 (the present (the present LLint int ))
DAFNE2, with 20 pbDAFNE2, with 20 pb-1-1 per point per point
comparison among the present BaBar analysis, an (O(1 ab-1)) BaBar update, and Lint = 20 pb-1
per energy point @ DAFNE-2, in the impact on hadhad :
: O(9%) | O(3%) | O(1%)
Babar systematic error: 6-8%
Stat error
Radiative Return @ 2.4 GeV
is the minimum polar angle of ISR photon. In the following, we will assume to tag the photon, with 20o.
is the overall efficiencym is the invariant mass of the hadronic system (,
…- x is 2E/s, s= e+e- c.m. energy - L0 is the total integrated luminosity
0
2
022
cos,1
2)11log)22((
)(
ϑ
−
−−
−
→−
Cx
LCx
CCxx
xL
L
N
born
hr
ISR differential luminosity
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ISR Luminosity for different c.m. energies (20o<160o)We integrated dL/dm for 25 MeV bin sizes.
[pb-1
/25 M
eV]
GeV
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With 2 fb-1 statistical error compatibile with present Babar data(the same we can expect for the systematic error) Not competitive with the Energy scan
Impact of DAFNE-2 on the range [1-2] GeV (3) using ISR @ 2.4 GeV
stat
istic
alst
atis
tical
had
had
h
adhad
s (GeV)s (GeV)
BaBar, with the published BaBar, with the published LLintint per point per point
BaBar, with 10 BaBar, with 10 (the present (the present LLint int ))
DAFNE-2, with 2 fbDAFNE-2, with 2 fb-1-1 @ 2.4 GeV @ 2.4 GeVcomparison among the present BaBar analysis, an (O(1 ab-1)) BaBar update, and Lint = 2 fb-1 at 2.4 GeVper energy point @ DAFNE-2, in the impact on hadhad :
: O(9%) | O(3%) | O(8%)
On the other channels theimprovement can be larger
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ISR Luminosity for different c.m. energies (20o<160o vs <15o(>165o))We integrated dL/dm for 25 MeV bin sizes.
[pb-1
/25 M
eV]
With 10 fb-1 and <15o(>165o) statistical error almost compatibile with 1 ab-1 Babar data. However very difficult to keep systematic error at 1% without detecting photon (closing the kinematics)
20o<160o <15o(>165o)
Different event topology btw 2.4 and 10.6 GeV:2+2-channel
Es=2.4 GeVs=10.6 GeV min
degrees
degreesGeV
GeV
E
• At 10.6 GeV:• Hard photon: E* = 3-5.3 GeV at s’ = 0-7 GeV.
No fakes from beam-gas processes.• Hadronic system collimated by
recoil.• Harder spectrum better
detection efficiency.
BABAR
• At 2.4 GeV:• Hard photon: E* < 1.1 GeV.• Distribution of particles and photon
“uniform” distributed
KLOE-2 gives an unique possibility to perform a test of SM via g-2 of muon and em. A measurement of 0.4% below 1 GeV and ~1-2% in the region 1-2.5 GeV is extremely important and would allow -by itself- to reduce the current error on aHLO
of a factor 2! (bringing the 2-3 sigma to ~5-6)ISR at 2.4 GeV can be useful for other physics item (i.e. , searches BSM, spectroscopy, etc…)The energy scan (ES) has been compared to ISR at 2.4 GeV. ES is statistically better than ISR, and if possible must be done. 10fb-1 at 2.4 GeV can be competitive with Babar at 1ab-1, especially with photon at SA. However the systematics must be studied!
Conclusions
spares
ISR @ 2.4 GeV vs scan - Assuming to tag the ISR , 2fb-1@ 2.4 GeV, translates in a luminosity
for single point in the range [100 nb-1 - few pb-1] which would correspond to [few hours - a day] of data taking with a scan @1032 cm-
2 sec-1 .
- 2fb-1 @ 2.4 GeV is statistically competitive with current results from B factories (90 fb-1). The much higher ISR probability of photon emission at lower s, compensates for the lower luminosity. However we should keep in mind that the planned luminosity of B factories is 1000 fb-1.
- In any case different systematics, background, etc…
ISR @ 2.4 GeV vs B-factories