15 January 2005 University of Chicago NSF Site Visit

Chicago CP Group: KTeV and Braidwood

• Overview of group • Status of KTeV analysis• Braidwood Neutrino Experiment

Ed Blucher

Current group members (KTeV + Braidwood): Faculty: Ed Blucher Senior research associate: Rick Kessler* (25% for 2005, 0% after) Postdoc: Matt Worcester, ongoing search Grad students: Erin Abouzaid, Elizabeth Worcester* Undergraduate students: Abby Kaboth, Jennifer Seger, David Underwood

Recent departures: Sasha Glazov (postdoc); now at DESY Val Prasad (Blucher student): now at Yale Colin Bown (Blucher/Winstein student): now at UT Austin Jim Graham (Blucher student): now at Catalyst

* only KTeV+ Kelby Anderson, Jim Pilcher on Braidwood

• Charged particle momentumresolution < 1% for p>8 GeV/c;momentum scale known to0.01% from K.

• CsI energy resolution < 1% forE > 3 GeV; energy scale knownto 0.1% from Ke.

The KTeV Experiment

E832: / to 10-4

E799: rare KLdecays to 10-11

(data taking:1996-2000)

Chicago NSF: CsI calorimeter, trigger, online and offline software

Chicago group physics analyses:

• + neutral K parameters (m, S, +, 00+) (Elizabeth Worcester dissertation)

• |Vus|: KL branching fractions, semileptonic form factors, radiative semileptonic decays

0e+e branching fraction (Erin Abouzaid dissertation)Semileptonic charge asymmetry massK* massKL+0 and KL000 form factors

To distinguish between direct and indirectCP violation, compare KL,S,:

1

/

/61

/Re0000

sL

sL

KK

KK

/ 0 direct CP violation

KL~ Kodd + Keven

“Direct”in decayprocess

“Indirect” from asymmetric mixing

: Indirect vs. Direct CP Violation:

00K K

0 0K K

(Blucher,Glazov,Graham,Kessler,Prasad,Worcester)

KTeV Result: Re() = (20.7 1.5(stat) 2.4(syst)) 10-4

= (20.7 2.8) 10-4

World average:Re() = (16.6 6) (confidence level = 10%)

A. Alavi-Harati et al (KTeV), Measurements of Direct CP Violation, CPT Symmetry, and Other Parameters in the Neutral Kaon System, Phys. Rev. D 67, 012005 (2003).

KL - KS Interference Downstream of Regenerator

KTeV Results:6 1

12

00

(5261 15) 10

(89.65 0.07) 10

0.61 0.62 (stat) 1.01 (syst)

0.39 0.22 (stat) 0.45 (syst)

S

SW

m s

s

History of KS Lifetime and m Measurements

Current Analysis Vacuum beam (KL) Reg. Beam ("KS") 00 + 00 )stat

(106) (106) (106) (106) (10-4)96+97 11.2 3.4 19.4 5.6 1.51999 14.9 3.7 25.8 6.1 1.496-99 26.1 7.1 45.2 11.7 1.0

Improvement in systematics needed to take advantage of increase in statistics.

• Better treatment of nearby and overlapping clusters: E scale, E nonlinearity

• Better modeling of fringe field: calorimeter calibration, E nonlinearity

• Improved drift chamber alignment: calorimeter calibration, E nonlinearity

• Improved simulation of delta rays: pt distribution, neutral background estimate

• Better drift chamber performance (99) and track reconstruction: mass resolution improved by ~10%.

• Full treatment of photon angles in simulation and reconstruction: E scale, E nonlinearity

All improvements implemented; detailed data-MC comparisons underway.

K+ Analysis:Full data sample

K00 Analysis:“Seed block” energy distribution

Dat

a/M

C R

atio

Clu

ster

s / 0

.5 G

eV 2005Analysis

2002Analysis(published)

DataMC

“Bench Tests” with prototype drift chamber (DC) and full KTeV electronics to study pathologies observed in DC resolution.

DC wire

A New Determination of |Vus|

For first row, PDG quotes 2.2 deviation from unitarity:

2 2 21 0.0043 0.0019 (PDG 2002)ud us ubV V V

Interesting to revisit KL measurements (PDG fit values basedon averages of many old experiments with large errors)

Recent K+ measurement from BNL E865 consistent with unitarity.

Motivation:

(Blucher, Glazov, Kessler)

222

3

5

3(

191 (0)

2)EW K us K

KK

F S fV IG M

Determination of |Vus| in Semileptonic KL Decays

KTeV measures B(KLe) and B(KL)

KTeV measures form factors neededto calculate phasespace integrals

Rad. Corrections(theory)

Form factorat t=0(theory)

3 3

00 3

0 0 0000 3

3

0 0 0 0 000 000

/ ( ) / ( )

/ ( ) / ( )

/ ( ) / ( )

/ ( ) / ( )

/ ( ) / ( )

K Ke L L

Ke L L

Ke L L

Ke L L

L L

K K e

K K e

K K e

K K e

K K

33 000 0 00 000

3 3 3 3 000 3

0.9993

1Ke

K

Ke Ke Ke Ke Ke

B

To determine the semileptonic widths, we measure the following5 ratios:

These six decay modes account for 99.93% of KL decays, so ratiosmay be combined to determine branching fractions.

E.g.,

Features of Branching Fraction Analysis

•Each ratio measured in statistically independent data sample collected with a single trigger (samples sizes are 105 to 106 per decay mode)

•Each ratio measured in two data samples: “high intensity” (same data used for analysis) “low intensity” (no regenerator and 10 lower intensity) Result for each ratio based on sample with lower total uncertainty

•Monte Carlo simulation is used to correct for acceptance difference between pair of modes

•Simulation includes inner bremsstrahlung contributions for all decay modes with charged particles, so branching fractions include radiated photons.

• For KL, we do not use muon system.

• For KL, we do not reconstruct the decay.

Neutral Decay Modes

4 or 6 photon-like clusters are paired to reconstruct two or three neutral pions consistent with a single decay vertex.

(Analysis almostidentical to analysis.)

0 0 0 0 0 and L LK K

Comparison of dataand Monte Carlo kaonenergy distributions

Monte Carlo spectrum wastuned using KL+

events

For partially reconstructedmodes, high energy solutionis plotted

Data – MC Comparison for Radiative Photon Candidates

• Ke3() and K3(): KLOR written by T. Andre. Includes virtual and real photons.

• K(): PHOTOS

• K(): KTeV generator includes IB, but ignores direct emission.

Radiation changes Ke3 acceptance by 3%; effect on other modes is < 0.5%.

Modes Partial Width Ratio

K3 / Ke30.66400.00140.0022

000 / Ke30.47820.00140.0053

0 / Ke30.30780.00050.0017

/ Ke3(4.8560.0170.023)103

00 / 000(4.4460.0160.019)103

Measured Partial Width Ratios

Comparison of KTeV and PDG Branching Fractions

0 02 1 6Re( / )( )

( ) 1

L L

SLS

S L

B BK

K B

Determination of |+| Using B(KL)

KTeV: 32.228 0.005 0.009 10KTeV EXT

KL-KS Interference

2 522 2

3 3(1 ) (0)

192F K

K EW K us K

G MS C V f I

Semileptonic Form Factor Measurements

(to determine IK integrals)

2

2 4

0 0 2

2 2

1( ) (0) 1

2

( ) (0) 1 ,

where ( ) ( )K

t tf t f

M M

tf t f

M

t P P P P

IK depends on the two independent semileptonic FFs:

We use the following parametrization for f+ and f0:

Parameter

Value ()

+ 20.64 1.75

+ 3.20 0.690 13.72

1.31

Form Factor Results

Semileptonic Form Factors: 0

5 more precise than PDG

Summary of Vus Changes from KTeV Measurements

22 2

3

5

3(1 ) (0)

192F K

EW K usK K

G MS V If

Ke3 increases by 5%K3 doesn’t change

Compared to PDG:

Ie decreases by 1.7%I decreases by 4.2% (both include -1% shift from +)

|Vus| Results

|Vus| = 0.2252 0.0008KTeV 0.0021ext

KTeV error: branching fractions, form factors

Ext error: f+(0), KL lifetime, radiative corrections

For KLe: |Vus| = 0.2253 0.0023

For KL: |Vus| = 0.2250 0.0023

Averaging these results (accounting for correlations):

2 2 21 0.0018 0.0019ud us ubV V V

Comparison with Unitarity

theory

A 5 sigma difference!

“Vus” Publications

•T. Alexopoulos et al (KTeV), A Determination of the CKM Parameter |Vus|, Phys. Rev. Lett. 93, 181802 (2004).

•T. Alexopoulos et al (KTeV), Measurements of KL Branching Fractions and the CP Violation Parameter |+|, Phys. Rev. D 70, 092006 (2004).

•T. Alexopoulos et al (KTeV), Measurements of Semileptonic KL Decay Form Factors, Phys. Rev. D 70, 092006 (2004).

•T. Alexopoulos et al (KTeV), Measurements of the Branching Fractions and Decay Distributions for KL and KLe, Phys. Rev. D 71, 012001 (2005).

+ Chicago Sun Times, Science Blog, Newswise, ScienceDaily, etc.

T. C. Andre, Radiative Corrections in Decays, hep-ph/0406006,submitted to Eur. Phys. J. C.

03K

Neutrino Oscillations

• During last few years, oscillations among different flavors of neutrinos have been established; physics beyond the S.M.

• Mass eigenstates and flavor eigenstates are not the same (similar to quarks):

1 2 3 1

1 2 3 2

1 2 3 3

e e e eU U U

U U U

U U U

mass eigenstatesflavor eigenstates

• Raises many interesting questions including possibility of CP violation in neutrino oscillations.

• CP violation in neutrino sector could be responsible for the matter-antimatter asymmetry.

MNSP matrix

1 2

1 2 3

1 2 3

12 12 13 13

12 12 23 23

13

3

13 23

cos sin 0 cos 0 sin 1 0 0

sin cos 0 0 1 0 0 cos sin

0 0 1 sin 0 cos

?

0 sin co

CP

CP

ee e

i

i

U U Big Big

U U U U Big Big Big

U U U

U

Big Big Big

e

mall

e

S

23s

12 ~ 30° 23 ~ 45°sin2 213 < 0.2 at 90% CL

What is e component of 3 mass eigenstate?

What do we know?

normal inverted

•What is value of 13?

•What is mass hierarchy?

•Do neutrino oscillations violate CP symmetry?

P( e ) P( e ) 16s12c12s13c132 s23c23 sin sin

m122

4EL

sin

m132

4EL

sin

m232

4EL

Value of 3 central to these questions; it sets the scale for experiments needed to resolve mass hierarchy and search for CP violation.

Key questions

•Why are quark and neutrino mixing matrices so different?

1

~ vs.

?

~ 1

1MNSP CKM

Big Big Small Small

U Big Big Big V

Sm

Small Small

Big Big Big Small Small

all

DNP, DPF, DAP, DPB Joint Neutrino Study on the Future of Neutrino Physics (2004)

We recommend, as a high priority, a comprehensive U.S. program to completeour understanding of neutrino mixing, to determine the character of the neutrinomass spectrum, and to search for CP violation among neutrinos. This programshould have the following components:

• An expeditiously deployed multi-detector reactor experiment with sensitivity to disappearance down to sin22 = 0.01, an order of magnitude below presentlimits.

• A timely accelerator experiment with comparable sin22 = 0.01 sensitivity andsensitivity to the mass hierarchy through matter effects.

• A proton driver in the megawatt class or above and neutrino superbeam with anappropriate very large detector capable of observing CP violation and measuring the neutrino mass-squared differences and mixing parameters with high precision.

e

(G. Barenboim and E. Blucher, co-leaders of Reactor Working Group)

Recommendation 2 (of 3):

Methods to measure sin2213

• Accelerators: Appearance (e)

• Reactors: Disappearance (ee) 2

2 2 1313( ) 1 sin 2 sin very small terms

4e e

m LP

E

22 2 2 213

23 13 13( ) sin sin 2 sin not small terms ( , ( ))4e CP

m LP sign m

E

Use fairly pure, accelerator produced beam with a detector a long distancefrom the source and look for the appearance of e events

T2K: <E> = 0.7 GeV, L = 295 km NOA: <E> = 2.3 GeV, L = 810 km

Use reactors as a source of e (<E>~3.5 MeV) with a detector 1-2 kms awayand look for non-1/r2 behavior of the e rate

Reactor experiments provide the only clean measurement of sin22: no matter effects, no CP violation, almost no correlation with other parameters.(In combination with accelerator experiments, can resolve 23 degeneracy.)

90% CL exluded regions with no osc.signal 90% CL allowed regions with osc.signal

Reactor and accelerator sensitivities to sin22

sin22θ13 = 0.05, δCP=0, Δm2 = 2.5×10-3 eV2

(3 yr reactor, 5 yr T2K)

δCP=0, Δm2 = 2.5×10-3 eV2

(3 yr reactor, 5 yr Nova)

~200 m ~1300 m

2atmm 2

solarm

2 22 2 2 2

13 12( ) 1 sin 2 sin sin 2 sin4 4atm solar

e e

m L m LP

E E

How to improve on previous reactor experiments? (Chooz limit: sin22< 0.15 for m2=2.5103 eV2) Add an identical near detector

Eliminate dependence on reactor flux; only relative acceptance ofdetectors needed

Optimize baseline (1500 m) Larger detectors (5 ton 50 tons) Reduce backgrounds (Go deeper 100m 150 to 300m)

Past reactor measurements:

The Braidwood Experiment

Features of Braidwood site:

• 23.6 GW reactors – 7.17 GW maximum power• Flat: flexibility, equal overburden at near and far sites, surface transportation of detectors• Favorable geology (dolomitic limestone): good for excavation, low radioactivity (order of magnitude lower U, Th than granite)

Braidwood Collaboration

Argonne Nat. Lab.: M. Goodman, V. Guarino, L. Price, D. Reyna

Brookhaven Nat. Lab.: R. Hahn, M. Yeh, A Garnov, Z. Chang, C. Musikas

U. of Chicago: E. Abouzaid, K. Anderson, E. Blucher,* M. Hurowitz, A. Kaboth, D. McKeen, E. Pod, J. Pilcher, J. Seger, M. Worcester

Columbia: J. Conrad, Z. Djurcic, J. Link, K. McConnel, M. Shaevitz,* G. Zeller

Fermilab: L. Bartoszek, D. Finley, H. Jostlein, C. Laughton, R. Stefanski

Kansas State: T. Bolton, C. Borjas, J. Foster, G. Horton-Smith, N. Kinzie, J. Kondikas, D. Onoprienko, N. Stanton, D. Thompson

U. of Michigan: B. Roe

MIT: P. Fisher, R. Cowan, L. Osborne, G. Sciolla, S. Sekula, F. Taylor, T. Walker, R. Yamamoto

Oxford: G. Barr, S. Biller, N. Jelley, G. Orebi-Gann, S. Peeters, N. Tagg

U. of Pittsburgh: D. Dhar, N. Madison, D. Naples, V. Paolone, C. Pankow

St. Mary’s University: P. Nienaber

Sussex: L. Harris

U. of Texas: A. Anthony, M. Huang, J. Jerz, J. Klein, A. Rahman, S. Seibert

U. of Washington: J. Formaggio

•spokesperson

Goals: Flexibility, redundancy, cross checks•4 identical 65 ton fiducial mass detectors; 2 at near site, 2 at far site •“Two zone detectors”: inner zone with Gd-loaded LS and r=2.6 m; outer zone with mineral oil and r=3.5 m.• Movable detectors with surface transport for cross-calibration; vertical shaft access to detector halls•Oscillation measurements using both rate and energy spectrum• Full detector construction above ground• Near and far detectors at same depth of 450 mwe with flat overburden; deep near detector will allow measurement of sin2W.

Braidwood Baseline Design

Detectors and analysis strategy designed to minimize relative acceptance differences

6 meters

Shielding

Central zone with Gd-loadedscintillator surrounded by bufferregions; fiducial mass determinedby volume of Gd-loaded scintillator

Events selected based on coincidenceof e+ signal (Evis>0.5 MeV) ands released from n+Gd capture(Evis>6 MeV). No positionreconstruction; little sensitivity to E requirements.

To reduce backgrounds: depth + active and passiveshielding

,e p e n Neutrino detection by 8 of s; ~ 30 secn Gd MeV

Braidwood Experiment Projected Uncertainties and Sensitivity

3 year run

Baseline Cost and Schedule Estimates

Civil Construction (Hilton and Assoc. consulting firm, using U of C seed money)

Detectors (Bartozek engineering, ANL)

Schedule

2004 Engineering/R&D proposal submitted2005 Full proposal submission2007 Project approval; construction start2009 Start datataking

Four detectors with veto system + EDIA $18MContingency $5M

Construction + EDIA $34MContingency $8.5M

$42.5M

$23M

Braidwood Engineering / R&D Proposal

Exelon Letter of support: - Enthusiastic about project - No security and site access problems foreseen - 1st step was MOU on bore holes

Multi-institution proposal submitted to NSF and DOE (PI: Blucher, CO-PIs: Shaevitz, Bolton, Klein, Fisher)

Proposal requests funding to complete the design and engineering of the baseline project:

• Civil engineering design leading to RFP for a “Design and Build” • Detector engineering leading to full “Design Report”• Final development of stable Gd loaded scintillator

Budget:• Civil Engineering$525k• Detector Engineering $408k• Liquid Scint. $28k• Education and Outreach $78k

• Total $1039k

Using seed money ($100k) from University of Chicago, we’ve drilled bore holes to full depth (200m) at the near and far shaft positions.Detailed information on geology, ground water, radioactivity, density, etc.

• Bore hole study provides informationneeded for underground construction design; reduces required contingency

• Demonstrates willingness of Exelonto allow construction on their site.

First construction at Braidwood site (December 2004)

Chicago Braidwood Group Activities

• Software development and detector optimization studies - Matt Worcester co-leads the Braidwood Software and Background Group (with Tim Bolton)

• Front-end electronics, DAQ, trigger development - Jim Pilcher leads the Braidwood Electronics Group

• Liquid scintillator test cell

• Detector mechanical engineering (Pod): Calibration system and phototube support

• Braidwood site investigation

Small liquid scintillator test cell

Instrumented with CAMACADCs,TDCs, NIM electronics+ATLAS Tile Calorimeterelectronics system

We’ve performed initialstudies with cosmics andradioactive sources:Co, AmBe, Cf.

Gd Loaded Scintillator PhototubePhototube

60”

20”

Large test cell with 100 liter Gd-loaded central regionunder construction

ACRYLIC CYLINDER END PLATES MATCHDETECTOR VESSEL THICKNESS

Student training: KTeV and Braidwood experiments have provided exceptional opportunities for training graduate and undergraduate students.

Examples:Val Prasad: 2002 Fermilab Dissertation of the Year award. Now doingatomic physics at Yale.

Peter Shawhan: 1999 Fermilab Dissertation of the Year award. Working onLIGO at Caltech.

Abby Kaboth (current undergrad): Working on liquid scintillator studies for Braidwood. Goldwater scholarship winner.

David Underwood (current undergrad): Performing measurement of semileptonic charge asymmetry, KL attenuation for analysis

Jennifer Seger (current undergrad): Reactor experiment sensitivity studies;KTeV CsI energy calibration

CP Group Summary

•Group is completing KTeV analysis program and starting newprogram in neutrino oscillation physics.

•We play a leading role in both experiments.

•We have concentrated group’s efforts on small number of important physics topics that have an extremely broad impact in particle physics.

•Both KTeV and Braidwood experiments provide exceptionaltraining opportunities for undergraduates, grad students, postdocs,and faculty.