Measurement of pp scattering lengths in Kaon decays by NA48/2
Experiments NA48/1 & NA48/2
description
Transcript of Experiments NA48/1 & NA48/2
September 27, 2005Status Report, SPSC
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Experiments NA48/1 & NA48/2Experiments NA48/1 & NA48/2
Status Report (SPSC-2005-031)
CERN, Cambridge, Chicago, Dubna, Edinburgh, Ferrara, Firenze, Mainz, Northwestern, Perugia, Pisa, Saclay, Siegen, Torino, Vienna
Collaboration:
V.Kekelidze for
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Content
Introduction Rare decays in the experiment NA48/1 Search for direct CP-violation in the NA48/2 Test of PT: precise measurement of
the - scattering length Rare decay of charged kaons Leptonic & semileptonic decays Summary & request
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High Precision Study of Kaon & Hyperon Decays
Physics motivation for the experimentsPhysics motivation for the experiments
Search for new physics & tests of the SM High accuracy tests of low energy QCD (PT) Quantitative tests of various model predictions
• NA48/1 NA48/1
2000 Phase I (no spectrometer): KS & KL decays
2002 Phase II (high intensity run): KS & Hyperon decays
KS in fiducial volume: ~ 3.5 1010
• NA48/2 NA48/2 simultaneous K+ and K- beams
2003 – 2004 K in fiducial volume: > 2. 1011
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Rare decays in Rare decays in the experiment the experiment
NA48/1NA48/1
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Measurement of Br(KSe)
Br = (6.8 0.2stat 02sys)10-4
PDG value : (6.9 0.4)10-4
analysis finishedpaper preparationis in progress
is improved in precision~13’000
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0+e+e decays
BR= (2.57 0.12stat +0.10 –0.09 syst)10-4
in good agreement withour measurement:
BR= (0+e-e)=(2.510.03stat 0.09syst)10-4
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0+- decays
BR= (2.2 0.3stat 0.2 syst)10-6
102 decays32 3.0
background
most precise measurement
paper in preparation
KTEV:
(4.7+0.2-1.4 stat0.8sys)10-6
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R= N(0)/ N(0) R= (9.31 0.05stat 0.04 syst)10-2
new (preliminary)
Br(KS + - 0) submitted to PRL
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Search for direct Search for direct CP-violation CP-violation
in NA48/2in NA48/2
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Direct CP violation
in K± ± ± , K± ± 0 0 M(u) 1 + gu, u = f( )
g = g+ - g- = 2Ag<g>
(Ag ) < 210 – 4 (limited by statistics)
GoalGoal
g + - g -
Ag = ———— g+ + g -
Requirements to experiment:
• high statistics (~ few109 decays)• stability in time• set –up symmetry
*
oddE
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Measurements & predictions
10-6
|Ag|
Experimental precisions by 2005:Experimental precisions by 2005:
10-5
10-4
10-3
10-2
SMSM SUSYSUSYNewNew
physicsphysics
Ford et al. (1970)
HyperCP prelim. (2000)
TNF prelim. (2002)“neutral” mode
NA48/2proposal
SM estimates vary within an order of magnitude (few 10few 10-6-6……
8x108x10-5-5). Models beyond SM predict substantial
enhancement partially within the reach of NA48/2.
[[AAgg~10~10-3-3]]
“charged”“neutral”
Theory
Asymmetry in decay widthsexpected to be smaller than
in Dalitz-plot slopes(SM: ~10-7…10-6).
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NA48/2 method
– Two simultaneous K+ and K– beams, superimposed in space, with narrow momentum spectra;
– Detect asymmetry exclusively considering slopes of ratios of normalized U distributions;
– Equalize K+ and K– acceptances by frequently alternating polarities of relevant magnets.
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1cm
50 100
10 cm
200 250 m
vacuum tank
He tank+ spectrometer
magnetB+
K+
K-
K+
K-
NA48/2NA48/2 experiment configuration experiment configuration
114m decay volume
focusing beams
DFDFQuadrupole Quadruplet
beams coincide within <1mm
FDFD
FRONT-END ACHROMAT
PK spectra, 603 GeV/c
54 60 66
The simultaneous K+ and K- beams NA48 Set-Up
not to scale
TAX 17 TAX 18
~71011
ppp
2nd
ACHROMAT
BM
z
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20032003 run:run: ~ 50 days~ 50 days(~ 1 month stable conditions)(~ 1 month stable conditions)
20042004 run: ~ 60 daysrun: ~ 60 days
~ ~ 200 TB of data recorded200 TB of data recorded
NA48/2NA48/2 runs runs
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recorded events, 10 6 # of Super-Samples
Run K - + K 0 0 (complete cycles)
2003-I 670 20 SS0
2003-II 940 28 SS1-3
Statistics
data taken in 2004: calibrated, reprocessed & filtered
analysis started
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Super-samples 2003Super-samples 2003
Dates Sub-samples
Achromat A+ Achromat A–
K+ K– K+ K–
0 22.06-25.07 26 229.6229.6 125.9125.9 201.0201.0 114.0114.0
1 6.08-20.08 12 122.5122.5 68.168.1 135.1135.1 75.475.4
2 20.08-3.09 12 147.2147.2 81.881.8 105.5105.5 58.958.9
3 3.09-7.09 4 40.640.6 22.622.6 54.554.5 30.430.4
Total 54 Total events selected 1613.2
Statistics selected for Ag measurement, events x106
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Selected statistics 2003
U
|V|
even pionin beam pipe
Data-taking 2003: 1.61x101.61x1099 events selected
KK+ + : 1.03x10: 1.03x109 9 eventsevents
KK : 0.58x10: 0.58x109 9 eventsevents
odd pionin beam pipe
MM=1.7 MeV/c=1.7 MeV/c22
Events
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Beam movement in time
X, cm
Y,
cm
DCH1(upstream magnet)
K+ K
X, cm Typical scales:• beam movement in time ~2mm• beam width ~5mm
Y,
cm
0 0.4 0.8-0.4-0.8
0
0.4
0.8
-0.4
-0.8
X, cm
Beam profile @DCH1(a small fraction of data)
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Acceptance cancellation cancellation within a supersample
N(A+B+K+)N(A+B-K-)RUS=
Detector left-right asymmetry cancels in 4 ratios of KK++ over Kover K uu-spectra-spectra::
ZZ
XXYY
JuraJura
SSalevealeve
Achromats: KAchromats: K++ UUpp
Achromats: KAchromats: K++ Down Down
B+
B
Indexes of R’s correspond to• beamline polarity (U/D);• direction of kaon deviation in spectrometer magnet field (S/J)
• same deviation direction by spectrometer magnet in numerator and denominator;same deviation direction by spectrometer magnet in numerator and denominator;• data from 2 different time periods used at this stage.data from 2 different time periods used at this stage.
N(A+B-K+)N(A+B+K-)RUJ=
N(A-B+K+)N(A-B-K-)RDS=
N(A-B-K+)N(A-B+K-)RDJ=
R(u) = RUS RUJ RDS RDJ=N(1+4gu)
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Example of fits: supersample 1
U
U
U
U
U
22=38.1/38=38.1/38
22=37.5/38=37.5/38 22=50.5/38=50.5/38
22=35.6/38=35.6/38 22=34.8/38=34.8/38
AAUS=(2.4=(2.4±4.6)x10±4.6)x10-4-4
AADS=(8.2=(8.2±4.4)x10±4.4)x10-4-4
AAUJJ=(-=(-0.20.2±4.6)x10±4.6)x10-4-4
AADJ=(-=(-1.01.0±4.4)x10±4.4)x10-4-4
=(2.3=(2.3±2.2)x10±2.2)x10-4-4R(u)/N
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Time-stability (vs super-sample)Time-stability (vs super-sample)
0
5
10
15
20
-5
-10
-15
-20
x10-4
Monte-Carlo describeseffects of
permanent magnetic fieldsand differences of
beamline properties
(S-J)/2 (D-U)/2
left / right up / downset-up asymmetry:
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Stability vs kinematic variablesStability vs kinematic variables
0
10
20
30
40
-10
-20
-30
-40
g x10-4
0
20
40
60
80
-20
-40
-60
-80
g x10-4
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Result & systematicsConservative estimations
of systematic errors
Effect on
Δx104
Acceptance and beam geometry
0.5
Spectrometer alignment 0.1
Analyzing magnet field 0.1
π± decay 0.4
U calculation and fitting 0.5
Pile-up 0.3
Syst. errors of statistical nature
Trigger efficiency: L2 0.8
Trigger efficiency: L1 0.4
Total Total systematic error 1.31.3
Raw Corrected for L2 eff
SS0 0.0±1.5 0.5 ± 2.4
SS1 0.9±2.0 2.2 ± 2.2
SS2 -2.8 ± 2.2 -3.0 ± 2.5
SS3 2.0 ± 3.4 -2.6 ± 3.9
TotalTotal -0.2 ± 1.0 -0.2 ± 1.3
22 2.2 / 3 3.2 / 3
Combined result: Δx104
(3 independent analyses) L2 trigger systematics included
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Preliminary result: 2003 dataPreliminary result: 2003 data
Slope difference:Δg = (-0.2±1.0stat.±0.9stat.(trig.)±0.9syst.)10-4 = (-0.2±1.7)10-4
Charge asymmetry:Ag = (0.5±2.4stat.±2.1stat.(trig.)±2.1syst.) 10-4 = (0.5±3.8)10-
4
• systematic errors are conservative for preliminary result
• better control of systematics in 2004 due to: - more frequent polarity alternation
- better L2 performance
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specific features:one charged track (±) to measure
asymmetry
Lkr used for 0 0 identification
different acceptance (u) & large g0= 0.652 ± 0.033
Asymmetry in K± ± 0 0 preliminary result based on SS0-SS3 (~ 48 M decays)
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K 00 + 4
m
reconstruction algorithm
pairs of ’s should have a common vertex compatible withkaon decay
E1E2 (d12)2
LKr
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Reconstructed decays K± ± 0 0
K+
preliminary result based on SS0-SS3 (~ 48 M decays)
K-
~31M ~17M
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Data analyzed: SS-0,-12,-3
g0 = (2.2 2.2 stat)10-4
u
uu
g1
g1N)(RCC
u
u
u
R(u), 10-4 SS0
SS12
SS3
R(u), 10-4
R(u), 10-4
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Stability check & comparison with MC
left / right up / downset-up asymmetry:
MC
exper.
10-4
g0AS-AJ AU-AD
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Stability checks of obtained g0
PK Vz
day sample|V|
10-4
10-4
g0
g0
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Result (preliminary):
three analyses obtain very close results
A0g major systematics in 10-4 units: alignment (<
0.1) acceptance & beam geometry (< 0.1)
momentum scale (< 0.1)u-calculation & fit (< 0.4)
accidentals (< 1.0)L1 trigger (< 1.5), L2 trigger (< 0.4),
fit region (0.0025),LKr nonlinearity corrections (< 0.4)
A0g = (1.7 1.7stat 1.2trig 1.0syst 0.2extern)10-4
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Test of Test of PT :PT :precise measurement of precise measurement of the the -- scattering length scattering length
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Theory calculationpredicted by PT first principles (Weinberg 1966)G.Colangelo, J.Gasser, H.Leutwyler, NP B603(2001)125
scattering length
m + = - 0.0444 ± 0.001002a0
0a m + = 0.220 ± 0.00500a( - )
02a m += - 0.265±0.004 1.5%
Experimental measurements mesoatom lifetime (DIRAC) form-factors in Ke4 decays
for the first time: Geneva-Saclay (1977): 30,000 events
best measurement: BNL E865 (2001): 400,000 events
precision limited by statistics
00a| - |2
02a
= 0.216 ± 0.013stat ±0.002syst±0.002theor
00a m
~ 6 %
Statistics of NA48/2: > 1,000,000 Ke4 events
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measurement of from K (3)
simple model: N. Cabibbo, P.L.B 93(2004)121801
A threshold effect in M(00) has been observed (cusp structure) for the first time in NA48/2 thanks to
high resolution in energy high statistics
collectedindication to the re-scattering of + - 0 0
in the decay K + - 0 0 is related to
00a( - )
02a
00a( - )
02aNew way !
two loops approximation: N.Cabibbo, G.Isidori, JHEP03(2005)021
(I symmetry is foreseen)introduce I-breaking parameter = (m+
2 - mo2)/m+
2 = 0.065 M.Knecht, R.Urech, N.P. B519(1998)329;
G. Colangelo,J.Gasser,B.Kubis,A.Rusetsky: Kaon Mini-workshop (CERN-05)
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First Observation of the + - -thresholdin K M0 0 decays
M2(00), (GeV/c2)2 M2(00), (GeV/c2)2
4m2()= 0.0779(GeV/c2)2
~23M decays
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Fit quality Simple Cabibbo model:
axm+ = (a0 - a2)m+/3
2/D.F. = 420.1 / 148
= data - MC
Cabibbo, Isidori: two loop approximation;I- breaking (1 parameter)
(a0 - a2)m+, a2m+ , g0 , h+ , N
2/D.F = 154.8 / 146
…..+ pionium (1.61 0.66)10-5
2/D.F.=149.1 / 145
consistent with Z.Silagadze calc: 0.810-5
exclude pionium region 2/D.F.=145.5 / 139
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Results (paper in preparation):
two analysis (different MC & criteria) obtain very close results
m+ major systematics: acceptance (0.001)
trigger (0.001)fit region (0.0025)
LKr resolution & nonlinearity (0.001) track- separation (0.002)
taking into account uncertainty in theory ~ 5% (ext):
00a( - )
02a
m+ = 0.268 0.010stat 0.004syst 0.013ext
m+ = - 0.041 0.021stat 0.014syst
00a( - )
02a02a
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m+ = 0.220 0.006stat 0.004syst 0.003R 0.011theor
m+= 0.264 0.006stat 0.004syst 0.003R 0.013theor
Results (continuation):
taking into account uncertainty in R= A ++- / A+00
& theoretical constrains between
experimental uncertainty < 3% - limited by statisticswhich will be increased using 2004 data by factor ~ 4
00a( - )
02a
00a
00a &
02a
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K±+-e±ν (Ke4)
taking into account additional data (SS0 & 2004) it is expected in total:
> 1000k decays
background
selection:2003 data SS1-3: ~ 350k (background ~0.5%)
mproducts
expected precision in better than ±0.010stat
00a
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Cabibbo-Maksymowicz variables
background
, e have opposite sign for
K+ & K- (T.D. Lee and C.S.Wu –1966)
d5K-(m,me,,e,)= d5K+ (m,m e,,-e,+)
- line of flight in K rest frame
both K+ and K- decays are accumulated at similar experimental conditions this allows to tests CP, and CPT (for the fist time)
and provide reliable cross checks for possible systematic ancertainties
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Other Rare Decays Other Rare Decays of Charged Kaonsof Charged Kaons
SS1-3:~1 month of running in 2003
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GoalsGoals
Rare decays to test PT & search for ACP
K , K 0 DE
K e+ e, K + , Ke2
K l l+l
K 0 , K 0 l+l, … etc.
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K 0
PDG
T: 55 – 90 MeV
• Br=(2.750.15)10-4
DE contribution:• Br=(4.70.9)10-6
Interference term – possible source of
CPV
(order of magnitudehigher than others)
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Z=(M(ee)/MK)2M(± e+e-), GeV/c2
Statistics comparable to the World best sample at low background (1-2%)
K±±e+e- & K±±+-
K± ± e+e-.Statistics > PDG
Analyses are ongoing: form-factors study
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Leptonics & SemileptonicsLeptonics & Semileptonicsof Charged Kaonsof Charged Kaons
Special minimum-bias runs in 2003 & 2004
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Goals Goals
Leptonics & Semileptonic decays:
Ke3, K
3
BR’s to improve precision of |Vus|
& check CKM unitarity,
check -e universality
form-factors to search for fT, fS
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Results (preliminary)
• R(Ke3/K2) = 0.2505 0.0009stat 0.0012syst • R(K3/K2) = 0.1646 0.0006stat 0.0011syst • R(K3/Ke3) = 0.657 0.003stat 0.003syst
• R(Ke2/K2 )= 2.416 0.043stat 0.024syst 2003 run
• R(Ke2/K2 )= 2.453 0.046stat 0.026syst 2004 run
PDG = 2.45 0.11SM = 2.472 0.001
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Summary & RequestSummary & Request
Special minimum-bias runs in 2003 & 2004
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NA48/1 high precision results are obtained on Ks decays and hyperon
semileptonics, (analysis continues)
NA48/2 first results are obtained on charged asymmetry in both
K± ± +- and K± ± 00 decaysbased on 2003 data
achieved precision is limited by statistics
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NA48/2NA48/2(cont.)
A “cusp” structure has been observed
for the first time in K 0 0 decays
which allows to high precision measurement
of - scattering length Large sample of both signs of K±e4
decays provides good opportunity for
high precision measurements of - scattering length
& for the first time - various asymmetries
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Large statistics of K± decays is accumulated for the study
of various rare decays
Precise measurement of K± leptonics & semileptonics decays
contributes to the CKM unitarity & -e universality
checks
NA48/2NA48/2(cont.)
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2003 data-analysis ongoing
2004 data-calibrated, reprocessed & filtered-analysis has started
NA48/2NA48/2(cont.)
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Resources Request for 2006
• Data storage at CERN:
reserve CASTOR space
~ 5 TB for MC data
~ 30 TB for possible reprocessing (?),
• CPU power:
guaranteed share for ongoing analysis
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Spares
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Results on Ag
Other experiment data on Agc
BNL (1970): (- 7.0 ± 5.3)∙10-3
FNAL, HyperCP –2000 (preliminary) (2.2±1.5±3.7)∙10-3
Serpukhov data on Ag0
I.V.Ajinenko et al., PLB567(2003)159.: (5.1 ± 2.8 )∙10-3
G.A.Akopdzhanov, hep-ex/0406008 prelim.: (0.2 ± 1.9 )∙10-3
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Leptonic decay selection56 hour minimum-bias run in 2004
K e K
3.91064000
(missing mass)2 ,(GeV/c2)2(missing mass)2 ,(GeV/c2)2
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Matrix element described with 5 Cabibbo-Maksymowicz variables
d5(K+) (s,se) J(m,mecoscose) d(me)d(m)d(cos)d(cosed(
where s m se me
exchange K+ K-→ e+ e-
g’ ei
Ke4 form factors: mK
2 F1 = fsei + cos (fpe
if+ g) à la Pais-Treiman mK
2 F2 = g mK
2 F3 = hei
fit parameters: g, g’, h; with s g; ff gh g
K- vs K+ matrix element: d5(K-, m me e ) = d5(K+, m me e )
line of flight in K rest frame
e plane plane
e
e+
K+
Basic Ke4+ and Ke4
- form factors