1. A proposal to Study Rare Kaon Decays Augusto Ceccucci/CERN
at the CERN SPS
Augusto Ceccucci/CERN
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
March 27, 2006
Saclay - Orsay

2. Quark Mixing and CP-Violation
Cabibbo-Kobayashi-Maskawa (CKM) matrix:
Non-diagonal (e.g. Vus ≠0)
 Flavour Violation
3 or more quark generations
 CP-Violation in SM (KM)
Ng=2 Nphase=0  No CP-Violation
Ng=3 Nphase=1  CP-Violation Possible
e.g., Im lt= Im Vts*Vtd ≠ 0  CPV
March 27, 2006
Saclay - Orsay

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 ~ l Vcb ~ l2 A Vub ~ l3 A(r- ih) Vtd ~ l3 A(1-r- ih)
Sensitive to |Vtd| CP
Im lt = A2 l5 h
Re lt = A2 l5 r
March 27, 2006
Saclay - Orsay

4. Status of Unitarity Triangle
Sides+angles
Sides vs. CPV
Rare kaon decays are loop-dominated. They are a unique
probe of the sd transitions and provide independent CKM tests
March 27, 2006
Saclay - Orsay

5. The four golden modes of Kaon Physics
Short-distance contrib (Gsd /G)
Irreducible
theory err. on
amplitude
Total SM BR
K0Lp0 n n
>99% 1%
3  10-11
K+p+ n n
88% 3%
8  10-11
K0Lp0 e+e-
38%
15%
3.5  10-11
K0Lp0 m+m-
28%
30%
1.5  10-11
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
Adapted from G. Flavour in the LHC era, 5-7 Nov 05, CERN
March 27, 2006
Saclay - Orsay

6. K→p nn : Theory in Standard Model
charm
contribution
top
contributions
The Hadronic Matrix Element is measured and isospin rotated
March 27, 2006
Saclay - Orsay

7. Predictions in SM Standard Model predictions
This used to be the largest theoretical error
(+/ ). It was reduced by a NNLO calculation
A. Buras, M. Gorbahn, U. Haisch, U. Nierste hep-ph/ )
Standard Model predictions
BR(K+p+nn)  (1.6×10-5)|Vcb|4[sh2+(rc-r)2]  (8.0 ± 1.1)×10-11
BR(KLp0nn)  (7.6×10-5)|Vcb|4h2  (3.0 ± 0.6)×10-11
The errors are mostly due to the uncertainty of the CKM parameters and not to the hadronic uncertainties
March 27, 2006
Saclay - Orsay

8. Theory vs. Experiment SM Observable Theoretical error
Experimental error
B(K0Lp0 n n)
~3% ??
B(K+p+ n n)
~6%
~75%
AFB(B  Xsl+l-)
~8%
B(B  Xsg)
~10%
~9%
B(B  Xsl+l-)
~13%
~20%
AFB(B  K(*)l+l-)
~15%
~30%
B(B  (K(*),r,w)g)
~25%
~40%
B(Bs  m+m-)
B(B  K*l+l-)
~35%
Adapted from U. Flavour in the LHC era, 6-8 Feb 06, CERN
March 27, 2006
Saclay - Orsay

9. Intrinsic theory error
Combining information from BR(K+→p+ nn ) and BR(K0→p0 nn ) one obtains:
(Buras et al. hep-ph/ )
So for a 10% uncertainty on Pc,
one can extract, in priciple,
a 3.4%exp. determination of
sin2b from kaon decays.
It is currently 4.6% from B decays
March 27, 2006
Saclay - Orsay

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
March 27, 2006
Saclay - Orsay

11. MFV: Sensitivity to Z0 Penguin from Bobeth et a. (2005)
March 27, 2006
Saclay - Orsay

12. New Sources of Flavour Symmetry Breaking
Generic MSSM Enhanced EW Penguins
March 27, 2006
Saclay - Orsay

13. Experimental State-of-the-art
March 27, 2006
Saclay - Orsay

14. K+→p+ nn BR(K+ → p+ nn ) = 1.47+1.30-0.89 × 10-10
hep-ex/ PRL93 (2004)
AGS
Stopped K+
~0.1 % acceptance
BR(K+ → p+ nn ) = ×
Compatible with SM within errors
March 27, 2006
Saclay - Orsay

15. Setting the bar for the next generation of K+→p+nn experiments
E787/E949: BR(K+ → p+ nn ) = ×
Current constraint on r,h plane ?
100 events
Mean=SM
100 events
Mean=E787/949
March 27, 2006
Saclay - Orsay

16. K0L  p0nn : E391a Upper Limit 10% of RUN I Pencil beam
Expected background
from K0L decays: 0.02
Acceptance: 0.73%
BR(K0L  p0nn )<2.86 %CL
Preliminary (Ken
6 improvement over KTeV one day special run
2 improvement over published limit (KTeV Dalitz technique)
For the future: JPARC LOI-05
Recently, J-PARC made a call for proposals
March 27, 2006
Saclay - Orsay

17. K0S,L →p0 e+e- and K0S,L →p0 m+m-
BR(KS→p0ee)  10-9 = (stat) ± 0.8(syst)
PLB 576 (2003)
BR(KS→p0mm)  10-9 = (stat) ± 0.2(syst)
PLB 599 (2004)
KS →p0 mm
NA48/1
NA48/1
6 events, expected back. 0.22
7 events, expected back. 0.15
BR(KL → p0 ee ) < 2.8 × KTeV PRL93, (2004)
BR(KL → p0 mm ) < 3.8 × KTeV PRL86, 5425 (2001)
March 27, 2006
Saclay - Orsay

18. Constructive now favored by two independent analyses*
K0L→p0ee (mm) in SM
With the KS measurements, the KL BR can be predicted
* Interference between short- and long-distance physics*
(Isidori, Unterdorfer, Smith,
EPJC36 (2004))
Constructive now favored by two independent analyses*
Destructive
*G. Buchalla, G. D’Ambrosio, G. Isidori, Nucl.Phys.B672,387 (2003)
*S. Friot, D. Greynat, E. de Rafael,
hep-ph/ , PL B 595 *
March 27, 2006
Saclay - Orsay

19. Summary K+ p+nn K0L  p0nn K0L  p0ee(mm)
Already 3 clean events are published (E787/E949)
Experiment in agreement with SM within 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  p0nn
Large window of opportunity exists.
Upper limit is 4 order of magnitude from the SM prediction
First results E391a (proposed SES~ )
LOI to continue at J-PARC
KOPIO TERMINATED
K0L  p0ee(mm)
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
March 27, 2006
Saclay - Orsay

20. Proposal to Measure the Rare Decay K+p+ n n at the CERN SPS
CERN-SPSC
SPSC-P-326
Proposal to Measure the Rare Decay K+p+ n n at the CERN SPS
CERN, Dubna, Ferrara, Florence, Frascati, Mainz, Merced, Moscow, Naples, Perugia, Protvino, Pisa, Rome, Saclay, San Luis Potosi, Sofia, Turin
March 27, 2006
Saclay - Orsay

21. Background rejection Guidance: S/B = 10 ~10-12 rejection
1) Kinematical Rejection
2) Photon vetoes and PID (p-m)
Basic idea to reject K+ p+p0
P(K+) = 75 GeV/c
Require P(p+) < 35 GeV/c
P(p0) > 40 GeV/c It cannot be missed in
the calorimeter/photon veto
March 27, 2006
Saclay - Orsay

22. Backgrounds kinematically constrained
Decay BR
K+m+n (Km2)
0.634
K+ p+p0
0.211
K+ p+p+p-
K+ p+p0p0
0.070
Allows us to define the signal region
92% of K+ decays
K+p+p0 forces us to split it into two parts
Region I: 0 < m2miss < 0.01 GeV2/c4
Region II: < m2miss < GeV2/c4
March 27, 2006
Saclay - Orsay

23. Backgrounds not kinematically constrained
Decay BR
K+p0e+n
(Ke3)
0.049
Km3
0.033
Km2g
5.5×10-3
K+p+p0g
1.5×10-3
Ke4
4×10-5
Km4
1×10-5
They span accross the signal regions
Must rely on Particle ID and veto
8% of K+ decays
March 27, 2006
Saclay - Orsay

24. P-326 Detector Layout K+p+ n n p+ K+ ~11 MHz n 75 GeV/c n
Gigatracker p+ K+
~11 MHz n
75 GeV/c
800 MHz beam
p/K/p n
(KABES)
March 27, 2006
Saclay - Orsay

25. P-326 Detector Layout K+p+p0 p+ g K+ ~11 MHz g 75 GeV/c 800 MHz beam
Gigatracker g p+ K+
~11 MHz g
75 GeV/c
800 MHz beam
p/K/p
(KABES)
March 27, 2006
Saclay - Orsay

26. Signal & backgrounds from K decays / year
Total
Region I
Region II
Signal 65 16 49
K+p+p0
2.7±0.2
1.7±0.2
1.0±0.1
Km2
1.2±0.3
1.1±0.3
<0.1
Ke4
2±2
negligible
K+p+p+p- and other 3-tracks bckg.
1±1
Kp2g
1.3±0.4
Km2g
0.4±0.1
0.2±0.1
Ke3, Km3 ,others -
Total bkg
9±3
3.0±0.2
6±3
March 27, 2006
Saclay - Orsay

27. Summary Signal events expected per year@BR=8 10-11 Background events
65 (16 Region I, 49 Region II)
Background events
~9 (3 Region I, ~6 Region II)
Signal/Background ~ 8
S/B (Region I) ~5
S/B (Region II) ~ 9
For Comparison: In the written proposal we
quoted 40 to account for
some reconstruction and deadtime losses
March 27, 2006
Saclay - Orsay

28. New high-intensity K+ beam for P-326
Already
Available
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 (msterad)
 0.40
 16 40
Av. K+momentum <pK> (GeV/c) 60 75
K+ ~ 1.5
Mom. band RMS: (Dp/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
~45 (~27)
~24(~15)
Eff. running time / yr (pulses)
3 x 105
K+ decays per year
1.0x1011
4.8x1012
 48
March 27, 2006
Saclay - Orsay

29. Decay Tank Specification: 10-6 mbar Measurements: Conclusions:
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 l/s diffusion or
cryogenics pumps the requested
vacuum level can be achieved
Conclusions:
The existing decay tank can be used
March 27, 2006
Saclay - Orsay

30. Gigatracker qp PK qK Pp SPIBES: Dependence of the signal to
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) Pp PK qK qp
Two Silicon micro-pixel detectors (SPIBES)
Timing
Pattern Recognition
Improved KABES (micromegas TPC)
To minimise scattering in the last station
SPIBES:
X/X0 << 1%
Pixel size ~ 300 x 300 mm
s(p)/p ~ 0.4%
excellent time resolution
to select the right kaon track
Dependence of the signal to
background (from K+ p+p0 ) ratio
as a function of the gigatracker
time resolution
March 27, 2006
Saclay - Orsay 30

31. SPIBES (Hybrid Pixel) y x MeV
G. Anelli, M. Scarpa, S. Tiuraniemi
200 mm Silicon sensor (> e/h mip)
Following Alice SPD
Bump-bonding
Read-out chip
Pixel 300 mm x 300 mm
Thinned down to ~100 mm (Alice SPD 150 mm)
Beam surface ~ 14 cm2
Adapted to the size of the SPIBES
r-o chips
~125 mm Cfibre for cooling & support y x
2mm/bin
Station 1(pixels) 2(pixels) (FTPC)
Front End and R/O
considerations based on
the experience of the
CERN-PH/MIC and PH/ED Groups with the
ALICE SPD
March 27, 2006
Saclay - Orsay
MeV

32. KABES principle: TPC + micromegas
FTPC (KABES)
Tdrift1
Tdrift2
Micromegas
Gap 25 μm
KABES principle: TPC + micromegas
Pioneered in NA48/2
Tested in 2004 at high
intensity 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
March 27, 2006
Saclay - Orsay

33. Straw Tracker 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
March 27, 2006
Saclay - Orsay

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) (m+p)
2.3 m
Operate in high vacuum
Low X/X0 z y
7.2 m
X/X0 ~ 0.1% per view x
130 mm / hit
s(P)/P = 0.23%  0.005%P
s(q) ~ 50  20 mrad
Good space
resolution
7.2 m
Redundant
momentum
measurement
2 magnets:
270 and 360 MeV Ptkick
5.4 m
8.8 m
5 cm radius beam holes
displaced in the bending
plane according to the
75 GeV/c beam path
Veto for charged
negative particles
up to 60 GeV/c
March 27, 2006
Saclay - Orsay

35. RICH Layout
March 27, 2006
Saclay - Orsay

36. RICH as velocity spectrometer….
Resolution of a 17m P-326 RICH
(CKMGEANT)
March 27, 2006
Saclay - Orsay

37. …and RICH for p-m separation
March 27, 2006
Saclay - Orsay

38. NA48 LKr as Photon Veto Energy of photons from K+ p+p0
hitting LKr: > 1 GeV
GeV
Consolidation of the
safety/control system and
read-out under way
March 27, 2006
Saclay - Orsay

39. LKr efficiency measured with data
K+  p+ p0 collected by NA48 in 2004
Cluster not
reconstructed
Eg = 22 GeV
Pion
P=42 GeV/c
Photon
E=11 GeV
Expected
position
Events are kinematically selected.
p+ track and lower energy g are use to
predict the position of the other g
K+p+p0p0
March 27, 2006
Saclay - Orsay

40. Example: “hadronic” cluster of a photon
Expected energy: ~29 GeV
Deposited energy: ~9 GeV
Maximum energy ~300 MeV
Expected g position
Measured LKr inefficiency per photon (Eg > 10 GeV):
h = (2.8 ± 1.1stat ± 2.3syst) × (preliminary)
March 27, 2006
Saclay - Orsay

41. Beam test foreseen during
Idea for measuring inefficiency in the range 2 GeV < Eg< 10 GeV
Use of the NA48 set-up.
Photons produced by bremsstrahlung.
SPS can provide a suitable electron beam.
Beam test foreseen during
the 2006 SPS run
Kevlar
window
Magnet
Calorimeter
vacuum e- g
Electron beam
(25 GeV/c)
Bremsstrahlung
Drift
chambers
Calorimeter inefficiency below Eg < 5 GeV is not critical
March 27, 2006
Saclay - Orsay

42. ANTI-Photon Rings From: 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
March 27, 2006
Saclay - Orsay

43. Other Physics Opportunities
The situation is similar to NA48, which was designed to measure “only” e’/e but produced many more measurements
Accumulating ~100 times the flux of NA48/2 will allow us to address, for instance:
Cusp like effects (p-p scattering)
K+  p0 p0 e+ n
Lepton Flavour Violation
K+  p+ m+ e- , K+p- m+ e+, (Ke2/Km2)
Search for new low mass particles
K+  p+ X
K+  p+ p0 P (pseudoscalar sGoldstino)
Study rare p+ & p0 decays
Improve greatly on rare radiative kaon decays
Compare K+ and K- (alternating beam polarity)
K+/-  p+/-p0g (CPV interference)
T-odd Correlations in Kl4
And possibly, given the quality of the detector, topics in hadron spectroscopy
March 27, 2006
Saclay - Orsay

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
March 27, 2006
Saclay - Orsay

45. Summary Clear physics case Healthy competition worldwide:
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
NA e’/e
 NA48/ KS rare decays
 NA48/ Dg/g in K  3p
 P K+  p+nn
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!
March 27, 2006
Saclay - Orsay

46. Spare Slides
March 27, 2006
Saclay - Orsay

47. Stability and Systematics
Systematic uncertainties
Effect on Δx104
Acceptance and beam geometry
0.3
Spectrometer alignment
0.1
Analyzing magnet field
π± decay
0.4
U calculation and fitting
0.2
Pile-up
Total systematics
0.6
Trigger efficiency: L2
0.5
Trigger efficiency: L1
Control of
Detector
asymmetry
Control of
Beamline
asymmetry
March 27, 2006
Saclay - Orsay

48. NA48/2 (2003 data) K+/- p+/- p+p- K+/- p+/- p0p0
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
K+/- p+/- p0p0
Δg = (2.3 ± 2.8stat. ± 1.3trig.(stat.) ± 1.0syst. ± 0.3ext.)x10-4 =
(2.2 ± 3.1)x10-4
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/
Order of magnitude improvement
March 27, 2006
Saclay - Orsay

49. Observation of p-p scattering effect in K→3p decays
NA48/2 has made the first observation the of the charge exchange process +00 in the K00 decay.
1 bin = GeV2
30M events
NA48/2
PLB 633 (2006) hep-ex/
4mπ+2
K±±00
4mπ+2
G~|M0+M1|2
N. Cabibbo, hep-ph/ PRL (2004)
N. Cabibbo and G. Isidori, hep-ph/ JHEP 503 (2005)
M2(00) (GeV/c 2)2
March 27, 2006
Saclay - Orsay

50. Difference between p-p scattering length in I=0 and I=2 states
the pionium contribution has been
fixed to the prediction:
Z.K. Silagadze, hep-ph/
(a0 – a2)m has low sensitivity to pionium
(a0 – a2)m+ = ± 0.010(stat) ± 0.004(syst) ± 0.013(theor)
In agreement with theory (a0 – a2)m+ = ± (Colangelo 2001)
March 27, 2006
Saclay - Orsay

51. MAMUD To provide pion/muon separation and beam sweeping.
Iron is subdivided in 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
Pole gap is 2 x 11 cm V x 30 cm H
Coils cross section 10 cm x 20cm
March 27, 2006
Saclay - Orsay

52. Trigger & DAQ Total input to L0: 11 MHz L0 (example): L0 output:
> 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 ~40
Important synergies with LHC
to be exploited: for instance, the LHCb
TELL1 board
March 27, 2006
Saclay - Orsay

53. NA48@CERN Re e’/e = 14.7 ± 2.2 10-4 ’/ ’/ lower inst. intensity
Direct CP-Violation established
1996
Re e’/e = 14.7 ± 2.2 10-4
1997
1998
1999
2000
2001
2002
2003
NA48: ’/
’/
’/ lower inst. intensity
NA48/1 KS
NA48/1: KS KL
no spectrometer
NA48/2: K
Ave: Re e’/e = 16.7 ± 2.3 10-4
+ KL Rare Decays
First observation of
K0S →p0 e+e- and K0S →p0 m+m-
Search for Direct CP-Violation
in charged kaon decays
pp scattering: PLB 633 (2006)
(a0-a2)m+= /
NA48/2: K
2004
March 27, 2006
Saclay - Orsay

54. Straw Elements and Design
12 ns rise time
100 ns total width
2300 mm
Glue – 5m
12.5 m
0.2 m Al
9.6 mm
25 m
Gold plated Tungsten wire 30 m
Polycarbonate
spacer, 25 mg
Two double layers form a view
Gas mixture: 20%Ar+80%CO2
3 coordinates
4 coordinates
2 coordinates
1 coordinate
10 cm
To fit easily into decay volume
an octagonal shape is proposed
8.8 m
186.3 m
from T0
5.4 m
7.2 m
k12hika+ (Niels) 
About 2000 * 6 -> straws in total
March 27, 2006
Saclay - Orsay

55. hep-ph/
March 27, 2006
Saclay - Orsay

56. : Physics Motivation [1] Helicity suppressed decay [2] Decay Form of
: left-handed (in SM)
: spin 0
p0 copiously collected from K+  p+p0
[1] Helicity suppressed decay
(A) Neutrino mass : implies
(B) Neutrino type : Majorana neutrino  x2 larger branching ratio.
[2] Decay Form of
(B) Decay into different neutrino flavors :
(A) Sensitive to any hypothetical weakly-interacting neutrals.
[3] Cosmological Interests
Neutron star cooling model through pion pole mechanism :
March 27, 2006
Saclay - Orsay

57. Branching Ratio New upper limit (E949) :
2/3 sample Saturation at 3.5x106
1/3 sample
Conservative upper limit
# signal < 113 (90%CL) subtracting the non-Kp2 bkgnds;
New upper limit (E949) :
A factor of 3 improvement from the previous best result.
March 27, 2006
Saclay - Orsay