february 27, 2006lausanne1 physics introduction –rare kaon decays in the sm…. –…and beyond...
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February 27, 2006 Lausanne 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
February 27, 2006 Lausanne 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
GIM mechanism No FCNC at tree levelViolation at one loop depending on quark masses and CKM couplings
February 27, 2006 Lausanne 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
February 27, 2006 Lausanne 4
Status of Unitarity Triangle
• 95% confidence regions extracted using| Vub|/| Vcb|, εK, ΔmBd, ΔmBs and sin2β
ρ = 0.214 ± 0.047 η = 0.343 ± 0.028
• Constraints from | Vub|/| Vcb|, ΔmBd and ΔmBs compared with constraints from CP violating quantities in the kaon (εK) and in the B (sin2β) sectors
ρ = 0.181 ± 0.060 η = 0.404 ± 0.035
Rare kaon decays are loop-dominated. Assuming SM they provide strong independent constraints to the UT
February 27, 2006 Lausanne 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
February 27, 2006 Lausanne 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
February 27, 2006 Lausanne 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
February 27, 2006 Lausanne 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
February 27, 2006 Lausanne 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
February 27, 2006 Lausanne 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
February 27, 2006 Lausanne 11
MFV: Sensitivity to Z0 Penguinfrom Bobeth et a. (2005)
February 27, 2006 Lausanne 12
New Sources of Flavour Symmetry Breaking
Generic MSSM Enhanced EW Penguins
February 27, 2006 Lausanne 13
Experimental State-of-the-art
February 27, 2006 Lausanne 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
February 27, 2006 Lausanne 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
February 27, 2006 Lausanne 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%
February 27, 2006 Lausanne 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)
February 27, 2006 Lausanne 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*
February 27, 2006 Lausanne 19
Summary• K+
– 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
– Large window of opportunity exists.– Upper limit is 4 order of magnitude from the SM prediction– First results E391a (proposed SES~3 10-10)– LOI 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
February 27, 2006 Lausanne 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
February 27, 2006 Lausanne 21
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
February 27, 2006 Lausanne 22
Status of P-326 (a.k.a. NA48/3)
• Presented at the CERN SPSC in September 2005
• R&D Endorsed by CERN Research Board on December 2005 (subject to funding)
• Beam Test foreseen in August 2006• Still seeking groups to fund the RICH
counter• Seeking full approval by end of 2006….• …to be able to start data taking some time
in 2009-2010
February 27, 2006 Lausanne 23
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
February 27, 2006 Lausanne 24
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
February 27, 2006 Lausanne 25
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
February 27, 2006 Lausanne 26
P-326 Detector Layout
75 GeV/c800 MHz beam/K/p
K+
+
~11 MHz
Gigatracker
(KABES)
K
February 27, 2006 Lausanne 27
P-326 Detector Layout
75 GeV/c800 MHz beam/K/p
K+
+
~11 MHz
Gigatracker
(KABES)
K
February 27, 2006 Lausanne 28
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
February 27, 2006 Lausanne 29
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
February 27, 2006 Lausanne 30
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
February 27, 2006 Lausanne 31
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
February 27, 2006 Lausanne 32
Gigatracker
32
X/X0 << 1%
Pixel size ~ 300 x 300 mm(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
•FTPC (Improved KABES)•To minimise scattering in the last station
SPIBES:
Dependence of the signal to background (from K+ ) ratioas a function of the gigatracker time resolution
February 27, 2006 Lausanne 33
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
February 27, 2006 Lausanne 34
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
February 27, 2006 Lausanne 35
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
February 27, 2006 Lausanne 36
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
February 27, 2006 Lausanne 37
RICH Layout
February 27, 2006 Lausanne 38
RICH as velocity spectrometer….
Resolution of a 17m P-326 RICH(CKMGEANT)
February 27, 2006 Lausanne 39
…and RICH for - separation
February 27, 2006 Lausanne 40
NA48 LKr as Photon VetoEnergy of photonsfrom K hitting LKr: > 1 GeV
GeVConsolidation of thesafety/control system and read-out under way
February 27, 2006 Lausanne 41
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
February 27, 2006 Lausanne 42
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)
February 27, 2006 Lausanne 43
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
February 27, 2006 Lausanne 44
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
February 27, 2006 Lausanne 45
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
February 27, 2006 Lausanne 46
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
February 27, 2006 Lausanne 47
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
February 27, 2006 Lausanne 48
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!