Status of A g measurement in NA48/2 Status of A g measurement in NA48/2 DANE 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 Status of Direct CP violation measurement in K ± 3@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: - PowerPoint PPT Presentation
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Status of Ag measurement in NA48/2Status of Ag measurement in NA48/2
DANE 2004Luca Fiorini
Scuola Normale Superioreand INFN Pisa
on behalf of NA48/2 collaboration:Cambridge, CERN, Chicago, Dubna, Edinburgh, Ferrara, Firenze, Mainz, Northwestern, Perugia, Pisa, Saclay, Siegen, Torino, Vienna
Status of Direct CP violation measurement
in K±3 @NA48/2
– Search for direct CP violation in:
K± ±+-
K± ±00
– 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 (K3 with lost pion)● June-July 2003 data with different systematic effects
Spectrometer magnet current inversion: every 24h (every ~3h in 2004)Achromat magnet current inversoin: every 7 days
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 ≠B
down 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 p
kick), 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
Track Momentum Correction● and corrections applied:
P=p(1+)(1+qbp)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+M3)/2 to PDG value of K mass
● : corrects the misalignment (DCHs relative movement) by putting the difference between M+
3 and M3 to zero
Day-sample
b(M3-M+
3), keV
70 mDCH shift
K±±+-
Direct CP violation @ NA48/2 8
Kaon spectra and StatisticsK±±+-
Events
Events K+
K-
M3π, GeV/c2
Mass Resolution: 1.7 MeV
ALLK-K+
720
120
290
310
1120400ALL
19070SS3
450160SS2
480170SS1
Events per supersample (in 106)
Direct CP violation @ NA48/2 9
Acceptance CancellationsK±±+-
Physical asymmetries:● AS → slope of ratio N(K+,B
up)/N(K-,B
down)
● AJ → slope of ratio N(K+,B
down)/N(K-,B
up)
Apparatus-induced asymmetries: ● A+ → slope of ratio N(K+,B
up)/N(K+,B
down)
● A- → slope of ratio N(K-,B
up)/N(K-,B
down) Z
axis
(beam
dir
ect
ion)
Sale
ve
Jura
X axis
Top view of the setup
ASJ = (AS+AJ)/2 physics asymmetry
A± = (A++A-)/2 = (AS-AJ)/2 asymmetry induced by experimental setup
[ many of the effects observed in A± cancel in ASJ ]
Direct CP violation @ NA48/2 10
Asymmetry Stability Vs. K momentum
K±±+-
Statistical error of A : 2,7.10-4 Statistical error of Ag: 2,7.10-4