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Statusof
Is the CKM matrix the only
source of CP violation?Leo BellantoniFermilab Users' MeetingJune 2002
220
24
tcb xXVRKBr
where
eKBrR
W
042
2
sin2
3901.0
22
21
02.007.040.10
(Buchalla & Buras, Falk et. al., D'Ambrosio and Isidori)
05.051.1 txX
Hadronic effects well understood
K+
K+
+
Compare B- D0 e- :HQET vs data
K+
0.79 0.10
<0.032
(BNL)
From fit by D'Ambrosio and Isidore, PL B530 (2002) 108 using above constraints, |Vub / Vcb|, K, and m(Bd)
K+
The CKM result in the event of no new physics
K+
In SUSY, branching ratio could be up to 210% (conceivably, much more) of the Standard Model value, leading to the above CKM result Buras,Colangelo,Isidori,Romanino,Silvestrini Nucl.Phys B566(2000)3.
K+
In MSSM, branching ratio could be between 65 to 102% the Standard Model value, leading to the above CKM result Buras,Gambino,Gorban,Jager,Silvestrini Nucl.Phys B592(2001)55.
K+
Buras et.al. found an "unlikely" SUSY scenario that gives enhancements of Br(K+
) up to 3x the SM level
Baek,Jang,Ko,Park, Nucl.Phys., B609(2001)442 also show a SUSY scenario where Br(K+
) differs markedlyfrom the SM level
Hattori,Hasuike,Wakaizumi, Nucl.Phys., B592(2001)55 also found large branching ratio enhancements in their 4 generation model
D'Ambrosio and Isidori, Phys.Lett., B530(2002)108 discusses the case wherenew physics has led us to draw the wrongconstraint from Bd mixing
BNL E787 reports 2 clean events
With recent (, values, expect
BNL E949 (upgrade of E787) expects to see 5 - 10 events using stopped K+
Run has started Needs 2 more years worth of data Joint collaboration with CKM (FNAL / BNL / IHEP)
CKM plans to see 100 events using the Main Injector and decay in flight
1075.182.0 1057.1)(
KBr
PRL 88, 041803 (2002)
K+
10
10
103.1
108.0)(
KBr
at 3 level,
Other Physics
•Lepton flavor violationK+ ++e- K+ +-e+
K+ -+e+ K+ -++
K+ -e+e+
•T violation in K+ 0l+
•Search for pseudoscaler in K+ e+
•Direct CP violation in 3,
•Form factors in K+ +l+l-
ppp
pppT
Detection
Fiducial region limited by beam energy,background from K, use of RICH tomeasure + velocity, need for K++ vertex
M2MISS = M2
K(1 - p/pK) + m2(1 - pK/p) – ppK2
100 events @ 17% x 1.6% x (8 x 10100 events @ 17% x 1.6% x (8 x 10-11-11)) Need ~4 x 10Need ~4 x 101414 K K++ ! !
Initial momentum-selectedbeam (+, p, K+) P/P ~ 2%
RF deflection: Asin(t) A ~ 15 MeV/c
Transport L = (integer)c /f t then integer multiple of 2 for +
2nd RF deflection e.g. 180o outof phase: -Asin(t+t)
For +, no net deflection For K+, deflection is 2A sin(n /K) cos(wt+ n /K)
Stop + with beam plug, collect K+
X
X
86.4
m12
.9 m
RF separated K+ beam
Turtle/GEANT simulation: Debunched 22GeV beam (+2%) 33MHz of K+ per 4 x 1012 ppp 71% Kaon purity Total charged particle rate into detector
<50MHz; muon component is 7.4MHz Achieves baseline CKM requirements
Need 5MeV/m P kick for 1sec spill need superconducting cavities to
create the deflection
RF separated K+ beam
RF separated K+ beam
Expressed as BMAX on inner Nb surface:This result: 104mTOur design @ 5MeV/m: 77mTTESLA @25 MeV/m: 110mTTESLA @35 MeV/m: 160mT
RF separated K+ beam
A recent 1-cell test result
Q
P (MeV/m)
Our Design Goal ThermalBreakdown
Have similar results on 2 other small structures, but still need to improve
(And have lots of tricks to try for that)
SURFT
RR0
0 lim
Detection
What We Want:
K++
What We'll Get:
K++
Br = 63.5%Also K++
K++
0(undetected)
Br = 21.2%
K++
X (undetected)
A
Kinematics
+ Veto
Veto
Charged VetoLow Material
Momentum,direction & position
of K+ and +
Detection
Redundant measurements essential
Tracking vs. RICHs
Straw Tubes
•Mechanical stress and leak rate testing2 x 10-7 atm-cc/sec-straw (N2)
•Fe55 source used to locate active region, wiresTypically 0.002" from nominal
•Ru106 source to measure drift times
20 straw prototypestesting in Lab 3
Photon Veto System
Small prototypes studied
2 sector (0.3%) prototype being
built now
Tagged e- beam test at Jlab Sept/Oct
20 layersscintillatorper PMT
4 PMTs persector in VVS
~4200 PMTsin entire vetosystem
We plan to explicitly test the factorizationhypothesis in an early special / engineering run
K+ 0+ Veto Test
We use the factorization to estimate the K+ 0+ background; i.e., we multiply overall 0 veto inefficiency of 1.6 x 10-7 by our kinematic rejection factor of 1/30000
BNL E787has testedfactorizationby plottingP(+) linein K+ +0
with (a) no veto cuts, (b)online vetocuts, (c) fullanalysis cuts
Electronics / DAQ
50MHz debunched beam need continuous deadtimeless digitization
TDC every (~30000) channel, QDC on , + vetos (~8000 channels)
Recent history of detector activity is important
Imagine 2 K++0 events 10ns PMT deadtime apart
K+
K+
+
+
(Branching Ratio)2 / (Number of veto channels)2
= 2 x 10-8 >> 8 x 10-11 Br we want to measure
Studying triggerless DAQ (just say yesand trigger at level 3 in software)
And at the end…
M2MISS = M2
K(1 - p/pK) + m2(1 - pK/p) – ppK2
Spares
Br(K+ ) = +{[ I(VtdVts
*) X(Mt/MW) ]2 CPV top loops
+[ R(VtdVts*) X(Mt/MW) CPC top loops
+R(VcdVcs*) P(Mt,s()) ]2}
Charm contribution; P = 0.42 0.06
+ =0.901
K+
32 Br(K+0e+)22 sin4W sin2C
Known to +2.5%
Charm contribution adds ~3% error in Br for any given I (VtdVts
*)
With current VCKM values
Br(K+ ) =(0.810.15)x10-11
(Hocker et.al., 2001)
(Buchalla & Buras)
RF separated K+ beam
Preliminary Specs
3.9 GHz, TM110 mode 15mm iris radius 47mm equator radius 38mm cell length
26 cells per meter 5 MeV/m Pkick; 15 MeV/station
Epeak= 19MV/m Bpeak= 77mT Transverse shunt impedance 702 /m Q x RSURF is 228 Stored energy 0.73 J/m 8.5 W/m dissipated into LHe 1.8 ~ 2.0 K Q: 2.2 x 109 (unloaded)
6.0 x 107 ( loaded )
Measuring the K+
UMS - high rate PWCs 2 stations of 6 planes each Rate 0.90 MHz/cm≲ 2 – compare
HyperCP rates of 0.75 MHz/cm2
K+ RICH - velocity spectrometer 10m long N2 radiator @ 1.1atmospheres
with ~10 detected photons 22GeV beam gives K+ resolution in () to
+0.5%
Measuring the +
20m long Ne RICH @ 1atmosphere:
Straw Tube tracker:
(total 13 layers)
K+, + RICHs
22GeV beam gives K+ resolution in () to +0.5%
K+ RICH is 10m long CF4 (or N2) radiator with ~10 detected photons
+ RICH is 20m long Ne radiator with 3000 PMTs
Challenges include: Need 02 contamination at O(10-6) Low mass mirrors High rate (~1MHz) photomultiplier
tubes Gaussian tails in resolution to 5
orders of magnitude Drawing heavily on the SELEX
experience
SELEX RICH
cm
Photon Veto System
Design assumes the demonstrated performanceof BNL-E787 system (1mm Pb / 5mm Scintillator)for vetoing low energy (20 - 200 MeV) photons
• angle and E() correlated in K++0
50% coverage
• E() > 1GeV in VVS +0 events critical
Online monitoring is crucial ~ Twoseconds of undetected dead time intwo years of data taking blows the
inefficiency budget
Photon Veto System
Small prototypes studied
2 sector (0.3%) prototype being built now
Tagged e- beam test at Jlab Sept/Oct
• Events with an E() > 1GeV in VVS have the enter at ~30 mrad angle
• GEANT simulation says 3 x 10-5 inefficiency can be achieved over 1GeV
• Photoproduction effects (e.g., Pb K0) in > 1GeV region: Total cross section ~4mBarn 4 x 10-5 inefficiency – but most of those final states will be detected
•Engineering problems are formidable!
+ Veto
Need to reject 14-20GeV + from K+2
decays at O (10-5) level
What could make a + fake a + ?• + bremsstrahlung• + e+• DIS
Tested a 26 layer (41mm Fe) / (10mm scintillator) 0.6 x0.6 meter prototype in Nov 2000 at IHEP(Protvino) with ~19GeV momentum analyzed + beam:
• 12 x 2 segmentation• After cuts on shower shape, acceptance (3~4) x10-6, with acceptance 75.3%• Corresponding GEANT numbers are 2 x10-6, 69%