1 / 13

Status of A g measurement in NA48/2

Status of Direct CP violation measurement in K ±  3 p @ NA48/2. Status of A g measurement in NA48/2. Status of A g measurement in NA48/2. DA F NE 2004 L uca Fiorini Scuola Normale Superiore and INFN Pisa on behalf of NA48/2 collaboration:

prescott-adams
Télécharger la présentation

Status of A g measurement in NA48/2

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. Status of Direct CP violationmeasurement in K±3p@NA48/2 Status of Ag measurement in NA48/2 Status of Ag measurement in NA48/2 DAFNE 2004 Luca Fiorini Scuola Normale Superiore and INFN Pisa on behalf of NA48/2 collaboration: Cambridge, CERN, Chicago, Dubna, Edinburgh, Ferrara, Firenze, Mainz, Northwestern, Perugia, Pisa, Saclay, Siegen, Torino, Vienna

  2. Direct CP violation @ NA48/2 2 Main Goal and Data samples • Search for direct CP violation in: K±±+- K±±00 • Data for present analysis: • collected from August 6 to September 7, 2003 • divided in 3 supersamples (self-complete data set ~ 2 weeks period where all magnet exchange permutations have been done) • Additional data (not included in present analysis): • 2 tracks events (K3with lost pion) • June-July 2003 data with different systematic effects

  3. Lorentz-invariants si = (PK-Pi)2, i=1,2,3 s0 = (s1+s2+s3)/3 u = (s3-s0)/m2 v = (s2-s1)/m2 -1.2 < u < 1.2 If acceptances are equal for K+ and K-, Ag can be extracted by a linear fit N(u,K+,Bup)= R(u) = N(1+g+u)/(1+g-u) ~N(1+2gAgu) N(u,K-,Bdown) Measurement Principles Kinematics Dynamics p1 Matrix Element (K±3) |M(u,v)|2 ~ 1 + g±u +hu2+ kv2 CP Violation: Ag = (g+-g-)/(g++g-)≠0 Charged mode is statistically favored (~4:1) but neutral mode has a larger absolute value of g: • gc = -0.2154 ± 0.0035 (K±±+-) • gn= 0.652 ± 0.031 (K± ±00) Mk p3 p2 Direct CP violation @ NA48/2 3

  4. Asymmertry: Theory Vs. Experiment • Theoretical predictions for Ag: • (2~4) ·10-4Belkov(1989-1995) • (2.3± 0.6) · 10-6Maiani (1995) • ~ 10-5Scimemi (2003) • Agc=Agn · [1+O( w)] w= A½/A3/2 ~ 1/20 • Experimental Results: • BNL(1970): Agc= (-7.0±5.3) · 10-3 • FNAL, HyperCP (2000):Agc= (2.2±1.5±3.7) · 10-3 (Choong, PhD Thesis) • Protvino, ISTRA+: Agn= (-0.3±2.5) · 10-3(Denisov, Frontier Science 2002) • NA48/2 goal • dAg < 2·10-4 Direct CP violation @ NA48/2 4

  5. NA48/2 Beam Line Simultaneous K+ and K- focused beams with momentum 60±3 GeV/c Beams steered to coincide within <1mm at DCH1 1.3·1011p/s 114m decay volume y z Direct CP violation @ NA48/2 5

  6. NA48/2 Detectors Main detector components: • Kabes (MicroMega TPC) 1mm strips Max rate:2MHz/strip D X = 50 mm(drift) D Y = 80 mm(strips) D t = 0.7 ns • Magnetic spectrometer (4 DCHs): Dp/p(KBS) Dp/p(DCH) ~ 1% (60 GeV K) • Liquid Krypton EM calorimeter (LKr) DE/E = 3.2%/E  9%/E  0.42% • Hadron calorimeter, photon vetos, muon veto counters Direct CP violation @ NA48/2 6

  7. NA48 Strategy for Ag Spectrometer magnet current inversion: every 24h (every ~3h in 2004) Achromat magnet current inversoin: every 7days BASIC PRINCIPLE OF THE MEASUREMENT (K+,B up/down) and (K-,B down/up) acceptances are equal and cancel out in the ratio. Deviations from the principle • Bup ≠Bdown Imperfect field inversion Hall probes to measure magnet field • Non inversable mag. field (Earth field and res. magn. of the beam iron pipe) Measured in spring 2003 (10-4 pkick), corrected at software level. • Imperfect K+ K- beams coaxialityAcceptance cut around COG position. • Since UP and DOWN conditions are realized at different time, time instability right-left asymetric of detectors or trigger is dangereus. Direct CP violation @ NA48/2 7

  8. K±±+- Track Momentum Correction • andcorrections applied: P=p(1+)(1+qbp) P – corrected track momentum p – observed track momentum q – charge of the track b – sign of magnetic field • : corrects the magnetic field by putting the value(M+3+M3)/2 to PDG value of K mass • :corrects the misalignment (DCHs relative movement) by putting the difference betweenM+3andM3to zero b(M3-M+3), keV 70 m DCH shift Day-sample Direct CP violation @ NA48/2 8

  9. K±±+- K+ Events Mass Resolution:1.7 MeV M3π, GeV/c2 K+ K- ALL SS1 310 170 480 Events K- SS2 290 160 450 SS3 120 70 190 ALL 720 400 1120 Kaon spectra and Statistics Events per supersample (in 106) Direct CP violation @ NA48/2 9

  10. K±±+- ASJ = (AS+AJ)/2physics asymmetry A± = (A++A-)/2 = (AS-AJ)/2asymmetry induced by experimental setup [ many of the effects observed in A± cancel in ASJ ] Acceptance Cancellations Physical asymmetries: • AS → slope of ratio N(K+,Bup)/N(K-,Bdown) • AJ → slope of ratio N(K+,Bdown)/N(K-,Bup) Apparatus-induced asymmetries: • A+ → slope of ratio N(K+,Bup)/N(K+,Bdown) • A-→ slope of ratio N(K-,Bup)/N(K-,Bdown) Top view of the setup Saleve Jura Z axis (beam direction) X axis Direct CP violation @ NA48/2 10

  11. K±±+- 2/ndf 6/11 ASJ + offset = 0 ± 0,117.10-3 AS+offset AJ+offset Statistical error of Ag: 2,7.10-4 Statistical error of A : 2,7.10-4 2/ndf 6,7/11 A = (0,131 ± 0,117).10-3 A+ A- Asymmetry Stability Vs. K momentum (AS+AJ)/2 + offset PK, GeV/c PK, GeV/c (A++A-)/2 Direct CP violation @ NA48/2 11

  12. K±±+- 2/ndf 13,5/12 AS+offset AJ+offset 2/ndf 5,6/12 A+ A- Asymmetry Stability Vs. Time (AS+AJ)/2 + offset Day-sample pair Day-sample pair (A++A-)/2 Day-sample pair Day-sample pair Direct CP violation @ NA48/2 12

  13. K±±+- K±±00 Conclusions • More than109K±±+-decays in 1 month of 2003 data taking • The statistical error of Ag at this level of analysis is2.7·10-4 • Major sources of systematics identified, up to now the error dominated by statistics. • About 4·107K±±00decays have been collected. Very early stage of analysis of the CP-violation in this mode • The statistical error of Ag is about5·10-4 • RUN 2004, 60 days of data taking are on progress. • NA48/2 is NOT only direct CP violation, many other interesting analysis on progress Ke2 , Ke3 , Ke4 , p+gg , p+0g , ..... Direct CP violation @ NA48/2 13

More Related