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

KOPIO Beam and Constraints

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

Neutral Beam (neutrons) Collimated to Supress Halo

Vertical Collimation Scheme

Simulation of Neutron CollimationNominal beam Neutron Energy Spectrum

Prototype Cathode Strip Chamber

Preradiator R&DChambers, electronics, and scintillator prototyped.Mechanical design in progress.

4m

Extruded Scintillatorwith WLS fiber

KOPIO Prototype Measurements– Tagged Photon Beams

Preradiator Angular resolution:25 mr at 250 MeV/c

Shashlyk R&D

Shashlyk modules prototypedand tested in beams.Mechanical design in progress

APD

Shashlyk Beam Measurements

Simulation: Combined Energy Resolution

3%( )E GeV

σ

New Aerogel tiles

Catcher R&D

Modules prototyped andtested in beams.

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

Summary and Outlook

• KOPIO R&D is concluding successfully.• Advanced planning for the construction

phase is beginning.• US Agencies – NSF and DOE – are

cooperating well, and international partners are contributing substantially.