april 25, 2006munich mpi1 physics introduction –rare kaon decays in the sm…. –…and beyond...
TRANSCRIPT
April 25, 2006 Munich MPI 1
• Physics Introduction– Rare Kaon Decays in the SM….– …and Beyond
• Flavour as a probe of New Physics complementary to the high energy frontier
• Experimental state-of-the-art– Recent results and world-wide perspectives
• Description of the CERN proposal P-326– Technique– Status
A Proposal to Study Rare Kaon Decaysat the CERN SPS
Augusto Ceccucci/CERN
April 25, 2006 Munich MPI 2
Quark Mixing and CP-Violation
'
'
'
ub
cb
td
ud us
cd cs
ts tb
V
V
V V
d d
s s
b b
V
V
V
V V
Ng=2 Nphase=0 No CP-Violation
Ng=3 Nphase=1 CP-Violation Possible
Cabibbo-Kobayashi-Maskawa (CKM) matrix:
•Non-diagonal (e.g. Vus ≠0) Flavour Violation•3 or more quark generations CP-Violation in SM (KM)
e.g., Im t= Im Vts*Vtd ≠ 0 CPV
April 25, 2006 Munich MPI 3
CKM Unitarity and Rare Kaon Decays The unitarity of the CKM matrix can be expressed by triangles in a complex plane. There are six triangles but one is more “triangular”:
VudVub*+VcdVcb*+VtdVtb*=0
It is customary to employ the Wolfenstein parameterization: Vus ~ Vcb ~ Vub ~ iVtd ~ i
Sensitive to |Vtd|
Im t = 2 5 Re t = 2 5
CP
April 25, 2006 Munich MPI 4
Status of Unitarity Triangle
Rare kaon decays are loop-dominated. They are a unique probe of the sd transitions and provide independent CKM tests
Sides+angles Sides vs. CPV
April 25, 2006 Munich MPI 5
The four golden modes of Kaon Physics
Short-distance contrib (sd /)
Irreducible
theory err. on
amplitude
Total SM BR
KL >99% 1% 3 10-11
K 88% 3% 8 10-11
KLee 38% 15% 3.5 10-11
KL 28% 30% 1.5 10-11
Adapted from G. Isidori @ Flavour in the LHC era, 5-7 Nov 05, CERN
•Short distance dynamics:– W-top quark loops constitute the
dominant contribution:•The EW short-distance amplitude is common in the SM…•…but potentially different beyond SM•Important to address all these decays
April 25, 2006 Munich MPI 6
K→ : Theory in Standard Model
2 2
5 5
20 0L L 5
Im Re Re( ) ( ) ( ) ( )
Im( ) ( )
t t ct t c
tt
B K X x X x P X
B K X x
charm
contribution
topcontributions
2 08
2 4
3 ( )
2 sinKW
Br K er
The Hadronic Matrix Element is measured and isospin rotated
*
*
us
c cs cd
t ts td
VV VV V
NLO Calculation:Buchalla & Buras, 1993
April 25, 2006 Munich MPI 7
Predictions in SM ( ) 0.367 0.033( ) 0.012( ) 0.009( )c c c sP X m
This used to be the largest theoretical error(+/- 0.037). It was reduced by a NNLO calculation A. Buras, M. Gorbahn, U. Haisch, U. Nierste hep-ph/0508165)
The errors are mostly due to the uncertainty of the CKM parameters and not to the hadronic uncertainties
Standard Model predictions
BR(KBR(K++++) ) (1.6×10 (1.6×10-5-5)|V)|Vcbcb||44[[22+(+(cc--))22] ] (8.0 ± (8.0 ± 1.1)×101.1)×10-11-11
BR(KBR(KLL00) ) (7.6×10 (7.6×10-5-5)|V)|Vcbcb||442 2 ± 0.6± 0.6×10×10-11-11
April 25, 2006 Munich MPI 8
Theory vs. Experiment
SM Observable Theoretical error Experimental error
B(KL ~3% ??
B(K ~6% ~75%
AFB(B Xsll) ~8% ??
B(B Xs) ~10% ~9%
B(B Xsll) ~13% ~20%
AFB(B K(*)ll) ~15% ~30%
B(B (K(*))) ~25% ~40%
B(Bs ) ~30% ??
B(B K*ll) ~35% ~13%
Adapted from U. Haisch @ Flavour in the LHC era, 6-8 Feb 06, CERN
April 25, 2006 Munich MPI 9
Intrinsic theory error
Combining information from BR(K→ ) and BR(K→ ) one obtains: (Buras et al. hep-ph/0508165)
| |0.41
sin 20.34
sin 2
0.83
td c
ctd
c
c
c
c
V P
V P
P
P
P
P
So for a 10% uncertainty on Pc,
one can extract, in priciple,a 3.4%exp. determination ofsin2 from kaon decays.It is currently 4.6% from B decays
April 25, 2006 Munich MPI 10
Beyond Standard Model
• Compare two scenarios:– Minimal Flavour Violation
• All mixing governed by universal CKM matrix– No Extra Complex Phases
• Same operators as in SM • Different coefficients• Stringent correlation with B rare decays
– New sources of Flavour Symmetry Breaking ~ TeV scale• Extra phases can lead to large deviations from SM
predictions, especially for the CP-Violating modes
April 25, 2006 Munich MPI 12
New Sources of Flavour Symmetry Breaking
Generic MSSM Enhanced EW Penguins
April 25, 2006 Munich MPI 14
K+→+
BR(K+ → + ) = 1.47+1.30-0.89 × 10-10
•Compatible with SM within errors
hep-ex/0403036 PRL93 (2004)
Stopped K+
~0.1 % acceptance
AGS
April 25, 2006 Munich MPI 15
Setting the bar for the next generation of K+→+ experiments
100 eventsMean=SM
100 eventsMean=E787/949
Current constraint on plane
?
E787/E949: BR(K+ → + ) = 1.47+1.30-0.89 × 10-10
April 25, 2006 Munich MPI 16
K0L E391a Upper Limit
BR(K0L )<2.8610-7 90%CL
Preliminary (Ken Sakashita@KAON2005)6 improvement over KTeV one day special run2 improvement over published limit (KTeV Dalitz technique)
•For the future: JPARC LOI-05
•Recently, J-PARC made a call for proposals
10% of RUN I
•Pencil beam •Expected background from K0
L decays: 0.02
•Acceptance: 0.73%
April 25, 2006 Munich MPI 17
K0S,L →0 ee and K0
S,L →0
KS →0
BR(KS→0ee) 10-9 = 5.8 +2.8-2.3(stat) ± 0.8(syst)
PLB 576 (2003)
7 events, expected back. 0.15
BR(KS→0) 10-9 = 2.9 +1.4-1.2(stat) ± 0.2(syst)
PLB 599 (2004)
6 events, expected back. 0.22
NA48/1 NA48/1
BR(KL → 0 ee ) < 2.8 × 10-10 @90%CL KTeV PRL93, 021805 (2004)
BR(KL → 0 ) < 3.8 × 10-10 @90%CL KTeV PRL86, 5425 (2001)
April 25, 2006 Munich MPI 18
0 12L(K ) 10Br
0 12L( ) 10Br e e
Constructive
now favored by two independent analyses*
(Isidori, Unterdorfer, Smith,
EPJC36 (2004))
0 0L
0 0L
1.1 110.9
0.3 110.3
3.7 10
1.5 10
K e e
K
B
B
Destructive
0 0L
0 0L
0.7 110.6
0.2 110.2
1.7 10
1.0 10
K e e
K
B
B
*G. Buchalla, G. D’Ambrosio, G. Isidori, Nucl.Phys.B672,387 (2003)
*S. Friot, D. Greynat, E. de Rafael,
hep-ph/0404136, PL B 595*
K0L→0ee () in SM
With the KS measurements, the KL BR can be predicted* Interference between short- and long-distance physics*
April 25, 2006 Munich MPI 19
Summary• K+
– Already 3 clean events are published (E787/E949)– Experiment in agreement with SM within large errors– Next round of exp. need to collect O(100) events to be useful– Move from stopped to in flight technique (FNAL Proposal turned down by P5)– Proposal for in-flight decays: CERN P-326– Letter of Intent at J-PARC to continue the study with decays at rest
• K0L
– Large window of opportunity exists.– Upper limit is 4 order of magnitude from the SM prediction– First results E391a (proposed SES~3 10-10)– Proposal being prepared to continue at J-PARC – KOPIO TERMINATED
• K0L ee()
– Long distance contributions under good control– Measurement of KS modes has allowed SM prediction– KS rates to be better measured – Background limited (study time dep. Interference?)– 100-fold increase in kaon flux to be envisaged
April 25, 2006 Munich MPI 20
Proposal to Measure the Rare Decay K at the CERN SPS
CERN, Dubna, Ferrara, Florence, Frascati, Mainz, Merced, Moscow, Naples,
Perugia, Protvino, Pisa, Rome, Saclay, San Luis Potosi, Sofia, Turin
CERN-SPSC-2005-013 SPSC-P-326
April 25, 2006 Munich MPI 21
Background rejection
Guidance: Guidance: S/B = 10S/B = 10 ~~1010-12 -12 rejectionrejection
1) Kinematical Rejection
2) Photon vetoes and PID ()
Basic idea to reject K++0P(K) = 75 GeV/c
Require P() < 35 GeV/c
P() > 40GeV/c It cannot be missed in
the calorimeter/photon veto
2222 ||||||
||1
||
||1 KK
K
KKmiss PP
P
Pm
P
Pmm
April 25, 2006 Munich MPI 22
Backgrounds kinematically constrained
Decay BR
K+K2
)0.634
K++0 0.211
K+++- K+00
0.070
92% of K+ decaysAllows us to define the signal region
K+0 forces us to split it into two parts
Region I: 0 < m2miss < 0.01 GeV2/c4
Region II: 0.026 < m2miss < 0.068 GeV2/c4
April 25, 2006 Munich MPI 23
Backgrounds not kinematically constrained
Decay BRK+0e+
(K(Ke3e3))
0.049
KK33 0.033
KK22 5.5×10-3
K+++00
1.5×1
0-3
KKe4e4 4×10-5
KK44 1×10-58% of K+ decays
They span accross the signal regionsMust rely on Particle ID and veto
April 25, 2006 Munich MPI 24
P-326 Detector Layout
75 GeV/c800 MHz beam/K/p
K+
+
~11 MHz
Gigatracker
(KABES)
K
April 25, 2006 Munich MPI 25
P-326 Detector Layout
75 GeV/c800 MHz beam/K/p
K+
+
~11 MHz
Gigatracker
(KABES)
K
April 25, 2006 Munich MPI 26
Signal & backgrounds from K decays / year
Total Region I Region II
Signal 65 16 49
K++0 2.7±0.2 1.7±0.2 1.0±0.1
K2 1.2±0.3 1.1±0.3 <0.1
Ke4 2±2 negligible 2±2K++ and other 3-tracks
bckg.
1±1 negligible 1±1
2 1.3±0.4 negligible 1.3±0.4
K2 0.4±0.1 0.2±0.1 0.2±0.1Ke3,
K3 ,othersnegligible
Total bkg 9±3 3.0±0.2 6±3
April 25, 2006 Munich MPI 27
Summary
Signal events expected per year@BR=8 10-11
65 (16 Region I, 49 Region II)
Background events~9 (3 Region I, ~6 Region II)
Signal/Background ~ 8S/B (Region I) ~5
S/B (Region II) ~ 9
For Comparison: In the written proposal we quoted 40 events/year@BR=10-10 to account for some reconstruction and deadtime losses
April 25, 2006 Munich MPI 28
Beam:
Present K12
(NA48/2)
New HI K+
> 2006
Factor
wrt 2004
SPS protons per pulse on T10 1 x 1012 3 x 1012 3.0
Duty cycle (s./s.) 4.8 / 16.8 1.0
Solid angle (sterad) 0.40 16 40
Av. K+momentum <pK> (GeV/c) 60 75 K+ ~ 1.5
Mom. band RMS: (p/p in %) 4 1 ~0.25
Area at Gigatracker (cm2) 7.0 14 2.0
Total beam per pulse (x 107)
per Effective spill length MHz
MHz/cm2 (gigatracker)
5.5
18
2.5
250
800
60
~45 (~27)
~45 (~27)
~24(~15)
Eff. running time / yr (pulses)
3 x 105 3 x 105 1.0
K+ decays per year 1.0x1011 4.8x1012 48
New high-intensity K+ beam for P-326 AlreadyAvailable
April 25, 2006 Munich MPI 29
Decay Tank
• Specification: 10-6 mbar– Study performed with Monte
Carlo using Fluka and Gheisha
to simulate the hadronic
interactions with the residual gas.
• Measurements:– Vacuum test performed on the
existing tube of NA48.– A 10-5 mbar level reached
with only 1 pump.– With a few 50000 l/s diffusion or
cryogenics pumps the requested
vacuum level can be achieved
• Conclusions:– The existing decay tank can be used
April 25, 2006 Munich MPI 30
Gigatracker
30
X/X0 << 1%
Pixel size ~ 300 x 300 m(p)/p ~ 0.4% excellent time resolution
to select the right kaon track
Provide precise measurements on all beam tracks (out of which only ~6% are K+)Provide very good time resolution Minimise mass (multiple scattering and beam interactions)Sustain high, non-uniform rate ( 800 MHz total)
P
PK
•Two Silicon micro-pixel detectors (SPIBES)
•Timing•Pattern Recognition
•Improved KABES (micromegas TPC)•To minimise scattering in the last station
SPIBES:
Dependence of the signal to background (from K+ ) ratioas a function of the gigatracker time resolution
April 25, 2006 Munich MPI 31
SPIBES (Hybrid Pixel)
• 200 m Silicon sensor (>11 000 e/h mip)
– Following Alice SPD
– Bump-bonding
• Read-out chip
– Pixel 300 m x 300 m
– Thinned down to ~100 m (Alice SPD 150 m)
• Beam surface ~ 14 cm2
– Adapted to the size of the SPIBES
r-o chips
• ~125 m Cfibre for cooling & support y
x2mm/bin
2mm
/bin
Station 1(pixels) 2(pixels) 3(FTPC)
G. Anelli, M. Scarpa, S. Tiuraniemi
Front End and R/O considerations based on the experience of the CERN-PH/MIC and PH/ED Groups with the ALICE SPD
MeV
April 25, 2006 Munich MPI 32
FTPC (KABES)
driftE
driftETdrift
1
Tdrift2
Micromegas
Gap 25 μm
Micromegas
Gap 25 μm
KABES principle: TPC + micromegas Pioneered in NA48/2
Tested in 2004 at highintensity with 1 GHz FADC
In NA48/2 KABES has achieved: •Position resolution ~ 70 micron•Time resolution ~ 0.6 ns•Rate per micro-strip ~ 2 MHz
New electronic + 25µm mesh strip signal occupancy divided by 3
April 25, 2006 Munich MPI 33
Advantages:
• can (in principle) operate in vacuum decay volume• can be designed without internal frames and
flanges• can work in high rate of hits• good space resolution (~130 m/hit for 9.6 straw)
• small amount of material (~0.1% X0 per view)
but
no previous large straw system has been operated in high vacuum
Straw Tracker
April 25, 2006 Munich MPI 34
Downstream straw tracker 6 chambers with 4 double layers of straw tubes each (
9.6 mm) Rate: ~45 KHz per tube (max 0.5 MHz) (+)Low X/X0
Operate in high vacuum
X/X0 ~ 0.1% per view
Good space resolution
130 m / hit
(P)/P = 0.23% 0.005%P() ~ 50 20 rad
Redundant momentummeasurement
2 magnets:270 and 360 MeV Ptkick
8.8
m
7.2
m
7.2
m
5.4
m
Veto for chargednegative particlesup to 60 GeV/c
5 cm radius beam holes displaced in the bending plane according to the 75 GeV/c beam path
z
x
y
2.3
m
April 25, 2006 Munich MPI 36
RICH as velocity spectrometer….
Resolution of a 17m P-326 RICH(CKMGEANT)
April 25, 2006 Munich MPI 38
NA48 LKr as Photon VetoEnergy of photonsfrom K hitting LKr: > 1 GeV
GeVConsolidation of thesafety/control system and read-out under way
April 25, 2006 Munich MPI 39
LKr efficiency measured with data
Cluster not reconstruct
edE = 22
GeV
Pion P=42 GeV/c
Photon E=11 GeV
Expected
position
K+ collected by NA48 in 2004Events are kinematically selected. track and lower energy are use topredict the position of the other
+00
April 25, 2006 Munich MPI 40
Example: “hadronic” cluster of a photon
Expected position
Maximum energy ~300 MeVExpected energy: ~29 GeVDeposited energy: ~9 GeV
Measured LKr inefficiency per photon (Eg > 10 GeV): = (2.8 ± 1.1= (2.8 ± 1.1statstat ± 2.3 ± 2.3systsyst) × 10) × 10-5 -5 (preliminary)(preliminary)
April 25, 2006 Munich MPI 41
Beam test 2006• Idea for measuring inefficiency in the range 2 GeV < E< 10 GeV
– Use of the NA48 set-up.– Photons produced by bremsstrahlung.
– SPS can provide a suitable electron beam.
vacuum
Electron beam
(25 GeV/c)Bremsstrahlung
Kevlarwindow
Driftchambers
MagnetCalorimeter
e-
Calorimeter inefficiency below E < 5 GeV is not critical
Beam test foreseen duringthe 2006 SPS run
April 25, 2006 Munich MPI 42
ANTI-Photon RingsFrom: Ajimura et al., NIMA 552 (2005)
•Two designs under test:–spaghetti (KLOE)–lead/scintillator sandwich (CKM)
•Extensive simulation under way•A tagged photon beam is available in Frascati to test existing prototypes
April 25, 2006 Munich MPI 43
Other Physics Opportunities
• The situation is similar to NA48, which was designed to measure “only” ’/ but produced many more measurements
• Accumulating ~100 times the flux of NA48/2 will allow us to address, for instance:
1. Cusp like effects ( scattering)– K e
2. Lepton Flavour Violation K e , K e+, (Ke2/K2)
3. Search for new low mass particles – K X – K P (pseudoscalar sGoldstino)
4. Study rare decays 5. Improve greatly on rare radiative kaon decays6. Compare K+ and K- (alternating beam polarity)
– K (CPV interference)– T-odd Correlations in Kl4
7. And possibly, given the quality of the detector, topics in hadron spectroscopy
April 25, 2006 Munich MPI 44
Status of P-326 (a.k.a. NA48/3)
• Presented at the CERN SPSC in September 2005– Strong endorsement of the Physics Case– Review of the proposed technique
• 2006 R&D plan endorsed by CERN RB on December 05– Resources being appropriated
• Beam Test foreseen in Sept-Oct 2006– Measure LKr efficiency for 1-10 GeV photons– Equip a CEDAR counter with fast read-out
• Collaboration still open to new groups– RICH responsibility
• Seeking full approval by end of 2006….– Enter CERN Medium Term Plan
• …to be able to start data taking some time in 2009-2010
April 25, 2006 Munich MPI 45
Summary
• Clear physics case – The discovery of New Physics will dramatically increase the
motivation for searches of new flavour phenomena • Healthy competition worldwide:
– J-PARC SPS • Exploit synergies and existing infrastructures
NA48 ’/ NA48/1 KS rare decays NA48/2 g/g in K 3
P-326 • SPS
– SPS used as LHC injector (so it will run in the future)– No flagrant time overlap with CNGS– P-326 fully compatible with the rest of CERN fixed target
because P-326 needs only ~1/20 of the SPS protons• Join us!
April 25, 2006 Munich MPI 47
Direct CP-violation in KK
|M(u,v)|2 ~ 1 + gu + hu2 + kv2
Centre of mass frame
u = 2mK∙(mK/3-Eodd)/m2;
v = 2mK∙(E1-E2)/m2.
• Measured quantity sensitive to direct CP violation:
Slope asymmetry:
Ag = (g+-g-)/(g++g-)≠0
Lorentz-invariantsu = (s3-s0)/m
2;
v = (s2-s1)/m2;
si = (PK-Pi)2, i=1,2,3 (3=odd );
s0 = (s1+s2+s3)/3.
SM estimates vary within an order of magnitude (few 10few 10-6-6…8x10…8x10-5-5). Models beyond SM predict substantial enhancement
April 25, 2006 Munich MPI 48
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
April 25, 2006 Munich MPI 49
Stability and Systematics Systematic uncertainties
Effect on Δx104
Acceptance and beam geometry
0.3
Spectrometer alignment 0.1
Analyzing magnet field 0.1
π± decay 0.4
U calculation and fitting 0.2
Pile-up 0.2
Total systematics 0.6
Trigger efficiency: L2 0.5
Trigger efficiency: L1 0.4
Control of Detectorasymmetry
Control of Beamlineasymmetry
Jura Jura (Left)(Left)
A+A+
A- A- SalèveSalève(Right)(Right)
ZZ
XXYY
Achromats: KAchromats: K+ + UpUp
Achromats: KAchromats: K++ DownDown
B+B+
B-B-
April 25, 2006 Munich MPI 50
NA48/2 (2003 data)K Slope difference:Δg = (-0.7±0.9stat.±0.6stat.(trig.)±0.6syst.)x10-4 = (-0.7±1.0)x10-4
Charge asymmetry:Ag = (1.7±2.1stat.±1.4stat.(trig.)±1.4syst.)x10-4 = (1.7±2.9)x10-4
KSlope difference:Δg = (2.3 ± 2.8stat. ± 1.3trig.(stat.) ± 1.0syst. ± 0.3ext.)x10-4 = (2.2 ± 3.1)x10-4
Charge asymmetry: Charge asymmetry: [using g0=0.638 ]
A0g = (1.8 ± 2.2stat. ± 1.0trig.(stat.) ± 0.8syst. ± 0.2ext.)x10-4 =
(1.8 ± 2.6)x10-4
hep-ex/0602014; PLB 634 (2006)
Order of magnitude improvement
April 25, 2006 Munich MPI 51
Observation of scattering effect in K→3 decays
1 bin = 0.00015 GeV2
K±±00
4mπ+2
30M events
4mπ+2
NA48/2 has made the first observation the of the charge exchange process +00 in the K00 decay.
M2(00) (GeV/c 2)2
NA48/2PLB 633 (2006) hep-ex/0511056
N. Cabibbo, hep-ph/0405001 PRL 93121801 (2004)
N. Cabibbo and G. Isidori, hep-ph/0502130 JHEP 503 (2005)
~|M0+M1|2
April 25, 2006 Munich MPI 52
Difference between scattering length in I=0 and I=2 states
(a0 – a2)m+ = 0.268 ± 0.010(stat) ± 0.004(syst) ± 0.013(theor)
In agreement with theory (a0 – a2)m+ = 0.265 ± 0.004 (Colangelo 2001)
NA48/2PLB 633 (2006)
hep-ex/0511056
April 25, 2006 Munich MPI 54
MAMUD
Pole gap is 2 x 11 cm V x 30 cm H
Coils cross section 10 cm x 20cm
•To provide pion/muon separation and beam sweeping.
–Iron is subdivided in 150 2 cm thick plates (260 260 cm2 )
•Two coils magnetise the iron plates to provide a 5 Tm field integral in the beam region •Active detector:
–Strips of extruded polystyrene scintillator (as in Opera)
–Light is collected by WLS fibres with 1.2 mm diameter
April 25, 2006 Munich MPI 55
Trigger & DAQ
• Total input to L0: 11 MHz • L0 (example):
– > 1 hit hodoscope 73%– muon veto 24%– Photon Veto 18%– <2 EM quadrants & E<50 GeV
3%• L0 output:
– 3% x 11 MHz = 330 KHz Keep: L0 + Control + Calibration +
Spin-offs < 1 MHz• L1 in PC farm (à la LHCb) to
keep as much flexibility as possible
• Software trigger reduction ~40Important synergies with LHCto be exploited: for instance, the LHCbTELL1 board
April 25, 2006 Munich MPI 56
NA48@CERN
1997
1998
1999
2000
2001
2002
2003
NA48: ’/
’/
’/
’/ lower inst. intensity
NA48/1 KS
NA48/1: KS
KL
no spectrometer
NA48/2: K
1996
2004NA48/2: K
Re ’/= 14.7 ± 2.2 10-4
First observation ofK0
S →0 ee and K0S →0
Ave: Re ’/= 16.7 ± 2.3 10-4
+ KL Rare Decays
•Search for Direct CP-Violation in charged kaon decays• scattering: PLB 633 (2006) (a0-a2)m+= 0.268 +/- 0.017
Direct CP-Violation established
April 25, 2006 Munich MPI 57
Glue – 5m12.5 m0.2 m Al
9.6 mm
25 m
Gold plated Tungsten wire 30 m
Straw Elements and Design
8.8 m186.3 mfrom T0
5.4 m 5.4 m
7.2 m 7.2 mk12hika+ (Niels)
About 2000 * 6 -> 12000 straws in total
3 coordinates
4 coordinates2 coordinates
1 coordinate
10 cm
2300 mm
To fit easily into decay volume an octagonal shape is proposed
Two double layers form a view Gas mixture: 20%Ar+80%CO2
12 ns rise time100 ns total width
Polycarbonate spacer, 25 mg
April 25, 2006 Munich MPI 59
[1] Helicity suppressed decay
: Physics Motivation
/41)/(103)( 228000 mmmmBr
: left-handed (in SM)
0: spin 00
(A) Neutrino mass : implies .2/MeV 2.18 cm
[3] Cosmological InterestsNeutron star cooling model through pion pole mechanism :
0
(B) Neutrino type : Majorana neutrino x2 larger branching ratio.
210
[2] Decay Form of ""0 nothing
(B) Decay into different neutrino flavors :
(A) Sensitive to any hypothetical weakly-interacting neutrals.
10105 Br
0
0 copiously collected from K+
April 25, 2006 Munich MPI 60
New upper limit (E949) : A factor of 3 improvement from the previous best result.
Branching Ratio
7
90
107.2
14.1117.0
1
103.02
110 )(
Br
# signal < 113 (90%CL) subtracting the non-K2 bkgnds;
70 107.2 )( Br
Conservative upper limit
2/3 sample Saturation at 3.5x106
1/3 sample