1 / 20

Recent results of the NA48/2 experiment

Recent results of the NA48/2 experiment. Mauro Raggi LNF On behalf of the NA48/2 Collaboration PHI PSI 08 International Workshop on e + e - collisions Laboratori Nazionali di Frascati, Italy 7-10 April 2008. Outline. NA48 history and detector NA48/2 recent results in charged Kaon decays

oakley
Download Presentation

Recent results of the NA48/2 experiment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Recent results of the NA48/2 experiment Mauro Raggi LNF On behalf of the NA48/2 CollaborationPHIPSI 08International Workshop on e+e- collisions Laboratori Nazionali di Frascati, Italy7-10 April 2008

  2. Outline • NA48 history and detector • NA48/2 recent results in charged Kaon decays • BR and FF in K±→p±e+e- (New preliminary) • BR and kinematics in K±→p±gg (New preliminary) • Measurement of K±→p±e+e-g (New Final) • Lepton universality in RK=Ke2/Km2 • NA62 prospects for RK PHI PSI 08, LNF 7-10 April 2008

  3. NA62 2007 Ke2/K2 run 10 years of History • NA48(1997-2001):Direct CP-Violation in neutral K • Re(ε’/ε) = (14.7 ±2.2)·10-4 NA48/1(2002):Rare KS decays and hyperons NA48/2(2003-2004):Direct CP-Violation in charged K • Ag(K±→π±π+π-) = (-1.5±2.2)·10-4 • Ag(K±→π±π0π0) = (1.8 ± 1.8)·10-4 NA62(2007-?): • RK(Ke2/Ke2) PHI PSI 08, LNF 7-10 April 2008

  4. PK = 60±3 GeV/c Width ~ 5 mm K+/K-~ 1 mm 54 60 66 Simultaneous K±Beam ~71011 p/spill 400 GeV/c Simultaneous K+ and K- beams: Flux ratio:K+/K– ~ 1.8 largecharge symmetrizationof experimental conditions PHI PSI 08, LNF 7-10 April 2008

  5. LKr EM calorimeter Spectrometer - 4 Drift Chambers- Magnet Trigger Hodoscope NA48 detector layout PHI PSI 08, LNF 7-10 April 2008

  6. K±→l+l– Theoretical framework K  *  l+l–:suppressed FCNC process Usefull test for cPT dee/dz ~ P(z)·|W(z)|2 z=(Mee/MK)2, P(z) is a phase space factor Form-factor models: (2) D’Ambrosio et al. JHEP 8 (1998) 4, (3) Dubnickova et al. hep-ph/0611175 (1) polynomial: W(z) = GFMK2∙f0∙(1+z) (2) ChPT O(p6): W(z) = GFMK2∙(a++b+z) + W(z) (3)Dubna ChPT: W(z) = W(Ma, Mρ, z) (f0,) or (a+,b+) or (Ma,Mρ) determine a model-dependent BR PHI PSI 08, LNF 7-10 April 2008

  7. Measurement technique and goals • The BR is measured normalizing to K0D • To reject K0D background a Kinematic cut has been applied: Mee>140 MeV • This cut suppress the low Mee region (z<0.08), most interesting for model dependent BR determination • NA48/2 analysis goals • Model-independent BR(z>0.08) in visible kinematic range • Model’s parameters and BRs in full kinematic range PHI PSI 08, LNF 7-10 April 2008

  8. NA48/2 K±→p±e+e- data sample Kaon decay flux (2003+2004):K=1.701011 FlaviaNet ‘08BR(K2) used K±→p±e+e- K±→p±p0D 7146 events (Mee>140 MeV)Background = 0.6% (K0DK0De + particle misID) 12.23 mln events Background = 0.15% (K0D) PHI PSI 08, LNF 7-10 April 2008

  9. Raw fit results (preliminary) polynomial: W(z) = GFMK2∙f0∙(1+z) ChPT O(p6): W(z) = GFMK2∙(a++b+z) + W(z) Dubna ChPT:W(z) = W(Ma, Mρ, z) (1) (2) Analysis cut:z>0.08, or Mee>140MeV/c2 (3) Available data set unable to distinguish among models Model-Independent BRMI(z>0.08) can be computed by integrating dG/dz PHI PSI 08, LNF 7-10 April 2008

  10. Preliminary BR results (1) (2) (3) Including uncertainty due to the model dependence, (full z range) BR=(3.080.04stat0.04syst0.08ext 0.07model)10–7=(3.080.12)10–7 CPV parameter (first measurement! correlated K+/K– uncertainties excluded): (K±ee) = (BR+–BR–) / (BR++BR–) = (–2.1±1.5stat±0.3syst)% PHI PSI 08, LNF 7-10 April 2008

  11. BR(10-7) NA48/2 NA48/2 New “naïve” WA ‘08 ‘92 ‘75 ‘99 ‘08 ‘99 ‘00 ‘92 VMD models [PRD60 (1999) 053007] Results comparison PHI PSI 08, LNF 7-10 April 2008

  12. Relevant only @ low mgg K±→p±gg physics O(p4) in cPT:B=D=0;Aloop diagrams contribution, C WZW anomaly (10%) O(p6) in cPT: unitarity corrections can increase the BR by 30-40 %[G. D’Ambrosio and J. Portoles, Nucl.,Phys. B386 (1996), 403] PHI PSI 08, LNF 7-10 April 2008

  13. BR dependence on ĉ Both the BR and the mgg spectrum shape depend on ĉ: The spectrum dependence will be used to extract the ĉ value PHI PSI 08, LNF 7-10 April 2008

  14. K±→p±gg data sample Previous measurement by E787:BR=(1.10.32)·10–6 ĉ=1.8±0.6Based on 31 events 5 BG events 1164 candidates3.3% BG 1164 events in 40% of the full data ~40 times larger wrt to world sample BG mainly from ppg(IB) good agreement with MC O(p6), ĉ=2measurement of ĉ is ongoing Preliminary BR result: MC O(p6), ĉ=2 BR(O(p6),ĉ=2)=(1.070.04sta0.08sys)·10–6 PHI PSI 08, LNF 7-10 April 2008

  15. First observation of K±→p±e+e−g Never observed before Like in gg ĉ determines BR and meeg shape Theoretical expectation (Gabbiani 99):BR(K±→p±e+e−g)=(0.9-1.6)·10-8 Normalization channel: K±→ p±p0DKaon decay flux: K=1.48·1011 (’03-’04) • Event sample: • 120 candidates events with • 6.1% Background Model-independent BR(Mgee>260MeV/c2): BR(±e+e−g)=(1.19±0.12stat±0.04sys)·10−8 Using Gabbiani ChPT O(p4) model: ĉ=0.90±0.45 [final result published, PLB659 (2008) 493] PHI PSI 08, LNF 7-10 April 2008

  16. 404 events 534 events 112 events Ke2/Km2 measurement physics Test of lepton universality V-A couplings Within SM Theoretical prediction for RK=RK(0)(1+dRK)=(2.477±0.001)·10-5 PDG average: RK=(2.45±0.11)·10-5 Experimental error (4.5%) 100 times bigger wrt theoretical [V. Cirigliano and I Rosell, Phys.Rev.Lett.99:231801,2007] PHI PSI 08, LNF 7-10 April 2008

  17. SUSY LFV mechanism Ke2/Km2 SM SUSY If tanb=40 and MH+=500 GeV with |DR31|2= 5·10-4 The effect can be as high as 2% and therefore measurablePR D74 (2006) 011701 (A. Masiero, P. Paradisi, R. Petronzio) PHI PSI 08, LNF 7-10 April 2008

  18. Present status of NA48/2 Ke2/Km2 2003 data taking:- 1 month of data taking with downscaled trigger - trigger efficiency 2004 data taking:- 56 hours of dedicated run with minimum bias trigger - K2 background subtraction in Ke2 sample 2 new preliminary result by Na48/2:NA48/2 (‘03 data 4670 ev): RK=(2.416±0.043sta±0.024sys)·10−5 NA48/2 (‘04 data 3407 ev): RK=(2.455±0.045sta±0.041sys)·10−5 PHI PSI 08, LNF 7-10 April 2008

  19. NA62 2007 data taking Ke2/Km2 • Dedicated2007 data taking: • 4 months of data taking (excluding detectors prototype tests)- More than ~1105 Ke2 events collected- Aims to a precision better than 0.5 % on RK • Reduction of systematics • New beam and spectrometer configuration: • Kaon momentum: (60±3) GeV/c→(75.0 ± 2.5) GeV/c • PT kick from spectrometer magnet: 120 MeV/c→263 MeV/c • → improved missing mass resolution • → improved Ke2 / K2 kinematic separation • Direct measurement of K2 background and electron mis-identification probability • Minimum bias 1 track trigger (as for 2004 run) PHI PSI 08, LNF 7-10 April 2008

  20. Summary • Preliminary BRs in K→pee • BR=(3.080.12)10–7 (including model dependence errors) • BRmi(z>0.08)=(2.26±0.08)·10-7 • Preliminary BR of K→pgg • BR(O(p6),ĉ=2)=(1.070.04sta0.08sys)·10–6 • Final BR and FF of K→peeg • BR(±e+e−g)=(1.19±0.12sta±0.04sys)·10−8 • ĉ=(0.90±0.45) • Preliminary results and prospect in Ke2/Km2 • 2003 preliminary: RK=(2.416±0.043sta±0.024sys)·10−5 • 2004 preliminary: RK=(2.455±0.045sta±0.041sys)·10−5 • More than 110K Ke2 events collected in 2007 dRK/RK~0.5% PHI PSI 08, LNF 7-10 April 2008

More Related