View
215
Download
0
Category
Preview:
Citation preview
0 0KMeasurement of L
KOPIOπ νν→
Douglas BrymanUniversity of British Columbia
April 22, 2004 DOE OHEP Review of the BNL High Energy Physics Program
CP
2*
"Jarlskog invariant" J
12
Im2 ts tdV VA λλ
= −
Standard Model CP Violation
Super-clean processes will challenge the Standard Model:
*
*
| | , CKM
949
KOIm( ) PIOt
s
s td
L t td
VVVK
Vπ νπ νν
ν0 0
+ +
Κ
→
→
E
: Standard ModelK πνν→Negligible long distance effects. Top quark domiHadronic matrix elements (K ) fr
nancom
e.K e .π π ν→ →
s W +
t t
νν νν
( )0L
0
-11 8.0 1.1 Branching Ratio 10
Theoretical Uncert. (est.)
3.2 0.6
7% 2%
π νν π νν+ +
± ±
Κ → Κ →
u u
Z
d sW +
t
W +
u u
Z
d
d
W +
s νW +
ν, ,e µ τu
t
Buchalla and Buras, Nucl. Phys. B548, 309 (1999); Buras et al.,hep-ph/0402112; Isidori,hep-ph/307014.
Roles of K Measurements in Flavor Physicsπνν→
* ew physics could be revealed K .
:
*
New flavor physics in the sector may be very different from that in the secto b r:
s-d
If B - physics is consistent with the SM
IN πνν→
K would add crucial additional information; the complexity of the flavor sector beyond the SM
:
is
f deviations from the SM are indicated
πνν→
foreseen in many models.
SK andψ π ν ν→ →B K
SM
Differences sensitive to new physics – virtually free of uncertainties.
SCP asymmetry in Kψ→B
0 0
+
( )( )
L π ννπ νν+
Γ →Γ →
KK
0
+
+ 0
0L
L
(Buras et al. hep-ph/040211)
(Buras hep-ph/0310208)
"Enhanced" Z Penguins (K ) x 1; (
Minimal Fl
K )
av
or Viol.(K ) x 2; (K ) x 4
Multiple Higgs
Low
*
*
** Extra
x 12sin(
dimensi
2 )
on
0.69
s* energy
βΓΓ
Γ
= −
Γ
X
SUSY
*
*
Nir and Worrah, Phys. Lett. ,319 (1998)B423
0 0Experiments seeking K π νν→
0 00 0
0[ , ]
9( )R( ) 1.4 10
( )
[ Limit based on isospin and :
]LL
L
Grossman NirK
K xK all
Kν
νπ ν
π ν
π νν+ +
−Γ →→ ≡ <
Γ →
→
10 9
75.9 10
10 10
12
KTEV (FNAL) result:
KEK E391a : s.e.s.
KOPIO (BN 10 , >50 eventsL) : s.e.s.
x
goal
goal
− −
−
−
<
−• <
•
•
KOPIO seeks an improvement of 105 over present results.
0 0 0 3L 0 2L 0 0L
10
10
0.93
0.36
0.1255
Mode Branching RatK
K
K Others
i
o
0 0 Measurement Primary Backgrounds
x
xe
LK
π ππ νγπ π π
π νν
−
− + −
+ −
→
→
→
→
KOPIO: Measurement of K0L → π0νν̄
CONCEPTS
• Measure as much as possible:
Energy, position and ANGLE of each photon.
• Work in the C.M. system :
Use TOF to get the K0L momentum.
• Maximize Photon Veto Efficiency
• Maximize Intensity of Microbunched Beam
-3 -2
100 Tp/spill (Upgraded from present 70 Tp)2.7 s spill, 2.3 s interspill period25 MHz micro-buching frequencyBunch width 200psInte
Prot
rbunch extinction 10 1
on Beam:
"Kaon Be0
42.5 degrea
em"
k:
ta
−
8 L
11
e-off angle Soft momentum spectrum [0.5,1.5 GeV] 10 K / spill, 12 % decay
10 neutrons / spill
Nominal BeamParameters
Shashlyk calorimeter
2 X0 Preradiator
Beam γ veto
√
Scintillator
Paper + lead+ paper
WLS fiber
PM tube
50 m steeltapes
Vacuumtank
DS Veto
Barrel, US Veto
CP veto
0 0LK π νν→
Preradiator
0π γγ→+ -Reconstruct first e e
in "Preradiator" to point toK decay vertex in vacuum.
γ →
Calorimeter
K π νν+ +→KOPIO Technique: Lessons from
Common Problem: Similar background processes exceed signal >1010
• Measure everything! (energy, position, angle, time)• Eliminate extra charged particles or photons
* E949 π0 inefficiency < 10-6
* KOPIO π0 inefficiency < 10-8
• Suppress backgrounds below the signal * Predict backgrounds from data: dual cuts* Use “Blind analysis” techniques * Test predictions “outside-the-box”
• Evaluate candidate events with S/N function
0949 Veto and Kinematics (P,R,E...)
Veto Reversed Veto AppliedRa
n
Ba
ge vs. Energy Momentum
Dual cutsckground Suppression
:E π π
γγ γ
+ +→K
Max. vetoγ
Check for correlations
Missing mass (2Emiss1 Emiss
2 cosθ12) vs.Missing energy (Emiss
1 + Emiss2 )
0 0 0L K π π→Photon vetoing & Kinematics:
Suppress events with low energy photons
4 4 80 (10 )(10 ) 10πε − − −< = 0 0L K π νν→
KEK Photonuclear
2
4
~ 10 (20-100 MeV) ~ 10 (100-220 MeV)
60 10
γε
πε
−
−
−<
E787
Photon Vetoing
Charged Particle Vetoing0Example Background: L eπ νγ− +→K
signal in 4 below 200 keV
π−
π+
185 290 Momentum (MeV/c)
10-5
10-4
10-3
ε
PSI Measurement(Preliminary)
Data
MC
KOPIO Goal 4
5
4
4
NIM 359, 478 (1995)
KEK: 1 GeV/c________________________
Particle (3.2 0.9) 10
1.6 101.3 10
(6.0 0.6) 10________________________
e xx
e xx
ε
π
π
+ −
+ −
− −
− −
±
<
<
±
A
Plastic Scintillator
Key features of the KOPIO concept have been established:• Micro-bunching• Photon pointing, energy resolution• Vetoing – including charged particles, photons, catcher
Kinematic suppression of backgroundsGoal: >50 Events with S/N>2
0* * *
1 2.E vs E Eγ γπ−
0 0L K π νν→
0 0 0L K π π→
S/N=2
0 0 0 3L 0 2L 0 0L
10
10
0.93
0.36
0.1255
K 14
Estimated Background Levels Branchin
K 5
K 3 Others
g Ratio Bkg. Ev
ents
1
x
xeπ ππ νγπ π π
−
− + −
+ −
→
→
→
******* Signal: 49 Background: 24
12000 Hours; Acceptance 9 x 10-3
AGS Microbunching Beam testMicrobunch width Interbunch extinction
Measured the inter-bunch extinction ratio(flux between bunches/within bunch).Observed a ratio of ~3-4% (could be less)KOPIO requires ~ 10-3 - 10-2
Need to control power supply ripple
Studied the RF extraction mechanismproposed for KOPIO & measured a microbunch rms width of 244 ps --KOPIO requires a 300 ps rms
Also developed monitoring methods
Vacuum System R&D
Finite elementAnalysis
Current Design:Honeycomb vessel and endsAl core, domed endsSolid Be beam pipe
Prototype Cathode Strip Chamber
Preradiator R&DChambers, electronics, and scintillator prototyped.Mechanical design in progress.
4m
Extruded Scintillatorwith WLS fiber
KOPIO Funding and Support Partners
• NSF• RSVP MREFC and R&D• University groups
• DOE OHEP• BNL Physics Department group• Yale group
• DOE ONP; BNL CAD (and university groups)• Canadian agencies (NSERC, CFI, TRIUMF)• Japanese agencies• Others (Russia, Switzerland, Italy (INFN) )
DOE-Supported GroupsMajor Responsibilities
• Yale– Shashlyk Calorimeter– Neutral beam and other simulations
• BNL (CAD)– AGS upgrades, proton beam, target– Neutral beam
• BNL (PHYSICS)– Detector infrastructure and integration– Veto detector systems– DAQ system– Simulations
Recommended