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Measurement of R with KLOE-2

Measurement of R with KLOE-2. G.V. & F.N. 13/1/2010. Error budget on a  HLO .  a  HLO = 5.3=3.3(  s<1GeV)  3.9 (1<  s<2GeV))  1.2(  s>2GeV). ~75% (mostly 2  ). ~40%. ~55%. error 2. contributions. Very important also the region 1-2 GeV !!!. But . in the range < 1 GeV

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Measurement of R with KLOE-2

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  1. Measurement of R with KLOE-2 G.V. & F.N. 13/1/2010

  2. Error budget on aHLO aHLO=5.3=3.3(s<1GeV) 3.9(1< s<2GeV)) 1.2(s>2GeV) ~75% (mostly 2) ~40% ~55% error2 contributions Very important also the region 1-2 GeV !!! But in the range < 1 GeV contributes to 70% !

  3. A rough estimate for g-2 aexp- atheo,SM= (27.7 8.4)10-10 (3.3) [Eidelman, TAU08] 8.4= ~5HLO~3LbL6BNL 4 3 3 1.6NEW G-2 7-8if 27.7 will remain the same) FJ08 aHLO=5.3=3.3(s<1GeV) 3.9(1< s<2GeV) 1.2(s>2GeV) aHLO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) Precise measurement of HAD at low energies very important also for em !!!

  4. Comparison of error profiles for aem(MZ) and am Direct integration of energy points for aem(MZ) R at 1% in the region s < 10 GeV  improvement of ~3 in a(MZ) Use of Adler function (It allows to use pQCD in a safer way down to 2.5 GeV) for aem(MZ) 1% in the region 1<s < 2.5 GeV (which is known with 6% accuracy)  improvement of ~5 on a(MZ) as evaluated “today” by direct integration region 2m<s < 2 Direct integration of energy points for am • Extremely important region since its accounts for: • 80% of the total error on Da(5)had (using Adler function) • 95% of the tot error on am

  5. e+e- data: current and future/activities KEDR(3-5%, ~15%) KLOE-2(?) HAD ~3-5% ~7-15% ~6% ~1%

  6. Impact of KLOE-2 on inclusive measurement 20 pb-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 Lint (nb-1) • MEA, 14 points, Lett. Nuovo Cim.30 (1981) 65 • B antiB, 19 points, Phys.Lett.B91 (1980) 155 s (GeV) s (GeV)

  7. Can KLOE-2 measure R with 1% error in the region 1-2 GeV? • 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?

  8. Impact of DAFNE-2 on the range [1-2] GeV (2p) BaBar, with the published Lint per point BaBar, with 10  (the present Lint ) DAFNE-2, with 20 pb-1 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 d(Dahad) /Dahad: • 2p+2p- : O(2%) |O(0.7%)|O(0.5%) Stat error Babar systematic error: 5% on 2 (8-14% for 2 statistical dshad / shad (%) s (GeV)

  9. Impact of DAFNE-2 on the range [1-2] GeV (2K2p) 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 d(Dahad) /Dahad : p- p+K- K+: O(15%) |O(5%)|O(3%) BaBar, with the published Lint per point BaBar, with 10  (the present Lint ) DAFNE-2, with 20 pb-1 per point statistical dshad / shad (%) Stat error Babar systematic error: 10% s (GeV)

  10. Impact of DAFNE-2 on the range [1-2] GeV (3p) BaBar, with the published Lint per point BaBar, with 10  (the present Lint ) DAFNE2, with 20 pb-1 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 d(Dahad) /Dahad : p- p+ p0: O(9%) |O(3%)|O(1%) statistical dshad / shad (%) Stat error Babar systematic error: 6-8% s (GeV)

  11. Radiative Return @ 2.4 GeV ISR differential luminosity q0is the minimum polar angle of ISR photon. In the following, we will assume to tag the photon, withq0=20o. eis the overall efficiency m is the invariant mass of the hadronic system (p+p-, p+p- p0, 2 p0p+p-, 2 p+2p-, …) • x is 2Eg/s, s= e+e- c.m. energy • L0 is the total integrated luminosity

  12. ISR Luminosity for different c.m. energies(20o<160o) We integrated dL/dm for 25 MeV bin sizes. [pb-1/25MeV] 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

  13. Impact of DAFNE-2 on the range [1-2] GeV (3p) using ISR @ 2.4 GeV BaBar, with the published Lint per point BaBar, with 10  (the present Lint ) DAFNE-2, with 2 fb-1 @ 2.4 GeV comparison 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 d(Dahad) /Dahad : p- p+ p0: O(9%) |O(3%)|O(8%) statistical dshad / shad (%) On the other channels the improvement can be larger s (GeV)

  14. ISR Luminosity for different c.m. energies (20o<160o vs <15o(>165o)) We integrated dL/dm for 25 MeV bin sizes. <15o(>165o) 20o<160o [pb-1/25MeV] 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)

  15. Different event topology btw 2.4 and 10.6 GeV: 2p+2p-channel s=2.4 GeV Eg min(qg,p) s=10.6 GeV BABAR • At 10.6 GeV: • Hard photon: Eg* = 3-5.3 GeV at s’ = 0-7 GeV. Þ No fakes from beam-gas processes. • Hadronic system collimated by recoil. • Harder spectrumÞ better detection efficiency. GeV degrees Ep • At 2.4 GeV: • Hard photon: Eg* < 1.1 GeV. • Distribution of particles and photon “uniform” distributed GeV degrees

  16. Conclusions • 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!

  17. spares

  18. ISR @ 2.4 GeV vs scan • Assuming to tag the ISR g, 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

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