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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are needed to see this picture.

~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



KLOE-2(?)


are needed to see this picture.~1% ~3-5%HAD

~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%)



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)



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



ISR Luminosity for different c.m. energies (20o<160o)We integrated dL/dm for 25 MeV bin sizes.

[pb-1

/25 M

eV]

GeV



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)



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

Documents

Measurement of R with KLOE-2