4-th SNOLAB Workshop, August 15-17, 2005 at Sudbury

Yuri Kamyshkov Univ. of Tennesseekamyshkov@utk.edu

TRIGA reactor

We know: neutral matter oscillatesWe know: neutral matter oscillates

ee

e

BB

KK

00

00 strangeness

beauty

lepton flavor

lepton number ? |L|=2

nn baryon number |B|=2

There are no laws of nature that would forbid the transitions except the There are no laws of nature that would forbid the transitions except the conservation of "conservation of "baryon charge (number)baryon charge (number)":":

M. Gell-Mann and A. Pais, Phys. Rev. 97 (1955) 1387 L. Okun, Weak Interaction of Elementary Particles, Moscow, 1963

nn

2003, M. Shiozawa28th International Cosmic Ray Conference

Prize the work of Super-K, Soudan-2, IMB3, Kamiokande, FrPrize the work of Super-K, Soudan-2, IMB3, Kamiokande, Fréjuséjus

All modes:baryon anti-leptonconserving (BL);searching for GUT and SUSY modesconserving (BL)

Unification of Forces and SUSYUnification of Forces and SUSY

To confirm SUSY and GUT ideas one should either discover To confirm SUSY and GUT ideas one should either discover super-symmetric particles or observe the proton decay.super-symmetric particles or observe the proton decay.

Although very attractive theoretically and supporting each other, Although very attractive theoretically and supporting each other, so far these ideas so far these ideas are notare not confirmed experimentally ! confirmed experimentally !

GUTGUT + SUSY+ SUSY

Important Theoretical Discoveries within Standard ModelImportant Theoretical Discoveries within Standard Model

• • Anomalous nonperturbative effects in the Standard Model lead to Anomalous nonperturbative effects in the Standard Model lead to violation of lepton and baryon number violation of lepton and baryon number (’t Hooft, 1976)(’t Hooft, 1976) thisthis B B and and LL nonconservation in SM is too small to be experimentally nonconservation in SM is too small to be experimentally observable at low temperatures, but it is large at T above electroweak scale.observable at low temperatures, but it is large at T above electroweak scale.

• “• “On anomalous electroweak baryon-number non-conservation in the On anomalous electroweak baryon-number non-conservation in the early universe” early universe” (Kuzmin, Rubakov, Shaposhnikov, 1985) (Kuzmin, Rubakov, Shaposhnikov, 1985)

The anomalous SM interactionThe anomalous SM interaction conservesconserves ((BBLL) but violate () but violate (B+LB+L). ).

Rate of anomalous (Rate of anomalous (B+LB+L)-violating electroweak processes at T > TeV )-violating electroweak processes at T > TeV

((sphaleron mechanismsphaleron mechanism) exceeds the Universe expansion rate. If ) exceeds the Universe expansion rate. If B = LB = L would would

be set at very high temperature (e.g. at GUT scale) due to some (be set at very high temperature (e.g. at GUT scale) due to some (BBLL) conserving ) conserving

interaction (e.g. by SU(5) SUSY proton decay), all quarks and leptons in the interaction (e.g. by SU(5) SUSY proton decay), all quarks and leptons in the

universe will be wiped out by (universe will be wiped out by (B+LB+L) -violating electroweak processes. ) -violating electroweak processes.

Baryogenesis can not be explained by (Baryogenesis can not be explained by (BBLL) conservation.) conservation.

•• N-nbar wN-nbar works within GUT + SUSY. orks within GUT + SUSY. First considered and developed within First considered and developed within the framework of Unification models the framework of Unification models ((R. Mohapatra and R. Marshak, 1979).R. Mohapatra and R. Marshak, 1979).

•• N-nbar was first suggested as a possible mechanism for explanationN-nbar was first suggested as a possible mechanism for explanation of BAU (Baryon Asymmetry of Universe ) of BAU (Baryon Asymmetry of Universe ) V. Kuzmin, 1970

•• The observed Baryon Asymmetry of the Universe The observed Baryon Asymmetry of the Universe ((A. Sakharov,1967)

tells us that Baryon number is not conserved, not tells us that Baryon number is not conserved, not GUT + SUSYGUT + SUSY •• ““The proton decay is not a prediction of the baryogenesis” The proton decay is not a prediction of the baryogenesis” ((Yanagida Yanagida @ @ 2002)2002)

•• If conventional (BIf conventional (BL)-conserving proton decay would be discovered L)-conserving proton decay would be discovered e.g. by Super-K, it will not e.g. by Super-K, it will not help us to understand BAU.help us to understand BAU.

etc. 00 ,Kp,Kp,ep

•• (B(BL) should be violated in Nature e.g. L) should be violated in Nature e.g. etc. ,n,,nn

•• In our In our laboratory samples: (#laboratory samples: (#pp + # + #nn # #ee))== (B (BL) is violated.L) is violated.

II dd ee aa ss oo ff 22 00 00 55 ’’ ss aa rr ee dd ii ff ff ee rr ee nn tt ff rr oo mm 11 99 88 00 ’’ ss ::

1 9 8 0 ’ s 2 0 0 5 ’ s

G U T m o d e l s c o n s e r v i n g ( B L ) w e r e t h o u g h t o w o r k f o r B A U e x p l a n a t i o n [ P a t i & S a l a m ’ 7 3 , G e o r g i & G l a s h o w ’ 7 4 … ]

“ P r o t o n d e c a y i s n o t a p r e d i c t i o n o f b a r y o g e n e s i s ! ” [ Y a n a g i d a ’ 0 2 ]

( B L ) 0 i s n e e d e d f o r B A U [ K u z m i n , R u b a k o v , S h a p o s h n i k o v ’ 8 5 … ]

N o i n d i c a t i o n s f o r n e u t r i n o m a s s e s m

0 [ … S - K ’ 9 8 , S N O ’ 0 2 , K a m L A N D ’ 0 3 ] a n d p o s s i b l e M a j o r a n a n a t u r e o f n e u t r i n o

G r e a t D e s e r t [ G i o r g i & G l a s h o w ’ 7 4 ] f r o m S U S Y s c a l e t o G U T s c a l e

N o D e s e r t . P o s s i b l e u n i f i c a t i o n w i t h g r a v i t y a t ~ 1 0 5 G e V s c a l e [ A r k a n i - H a m e d , D i m o p o u l o s , D v a l i ’ 9 8 … ]

( B L ) = 0 i n S M , S U ( 5 ) , S U S Y S O ( 1 0 ) … ( B L ) 0 i n e x t . S U S Y S O ( 1 0 ) , L - R s y m , Q G

E n e r g y s c a l e : 1 0 1 5 1 0 1 6 G e V E f f e c t i v e e n e r g y s c a l e : a b o v e T e V

., e tcKνp,πep 0 ., e tcν , nβ, , νnn R 02

Some Some (B(BL)L)0 nucleon decay modes (PDG’04)0 nucleon decay modes (PDG’04)

(BL)0 modes Limit at 90% CL S/B Experiment’year

>1.71031 yr 152/153.7 IMB’99

>2.11031 yr 7/11.23 Fréjus’91

>2.571032 yr 5/7.5 IMB’99

>7.91031 yr 100/145 IMB’99

>1.91029 yr 686.8/656 SNO’04

>7.21031 yr 4/4.5 Soudan-II’02

> 4.91025 yr Borexino’03

epp

een n

n

nn nn

nn with free neutrons in vacuum has highest future reach in (B–L)0 search

Bound n: J. Chung et al., (Soudan II) Phys. Rev. D 66 (2002) 032004 > 7.21031 years

PDG 2004:Limits for both free reactor neutrons andneutrons bound inside nucleus

123

2

10 where

s~R

R freebound

Free n: M. Baldo-Ceolin et al., (ILL/Grenoble) Z. Phys C63 (1994) 409

with P = (t/free)2

RR is “nuclear suppression factor” is “nuclear suppression factor”Uncertainty of Uncertainty of RR from nuclear from nuclear

models is ~ factor of 2models is ~ factor of 2

Search with free neutrons is squareSearch with free neutrons is squaremore efficient than with bound neutronsmore efficient than with bound neutrons

nnnbar transition probability nbar transition probability

level few eaccepatabl down to screened becan field mag.Earth

]measured!not [BTW CPT from follows as moment magnetic

0 :same theis and for tialgravipoten

ed)not violat is CPT (if

0 whereframe reference a is there

hold) is invariance-T (i.e.

2 ;

2

:operatorsenergy icrelativist-non are and where

system on then Hamiltonia H

state QMnbar -n mixed

22

nT

nμnnμ

UUΔUnn

mm

p

nnnn

Um

pmEU

m

pmE

EE

E

E

n

n

nn

nn

nn

nnnn

nn

nn

n

n

:sassumption Important

-mixing amplitude

All beyond the SMphysics is here

nnbar transition probability (for given )

nn

nnn

n

mmΔmt

V

tmV

mVtP

Vm

VmH

and ,experimentan in n timeobservatio is

tial)gravipoten ofpart or field; mag.Earth dcompensate-non todue (e.g.

neutron-anti andneutron for different potential a is where

)2(sin

)2( For

222

22

2

22

0 and 0 ns"oscillatio vacuum" theofsituation idealIn

nnnn

τ

tt

αPΔmV

]10[ timeon)(oscillatin transitiosticcharacteri is 23eVnn

e)flight tim of square sec,per used neutrons ofnumber (

2

2

tN

tN"ySensitivit"

n

n

At ILL/Grenoble reactor in 89-91 by Heidelberg-ILL-Padova-Pavia Collaboration M.Baldo-Ceolin M. et al., Z. Phys., C63 (1994) 409

Previous n-nbar search experiment with free neutrons

ss 1051:ysensitivit

106061 measured

1090 and m 90 ~ Lwith

292

18

.tN

.P

sec.t

nn

Detector of Heidelberg-ILL-Padova-Pavia Experiment @ILL 1991

No background! No candidates observed.Measured limit for a year of running:

sec106.8 7nn

= 1 unit of sensitivity

Scheme of N-Nbar search experiment with vertical layoutScheme of N-Nbar search experiment with vertical layout

Dedicated small-power research reactor with cold neutron moderator Vn ~ 1000 m/s

Vertical shaft ~1000 m deep with diameter >5 m

Large vacuum tube, focusing reflector, Earth magnetic field compensation system < 3 nT

Detector (similar to ILL N-Nbar detector) at the bottom of the shaft (no new technologies)

No background: one event discovery.

Not to scale

Annular core TRIGA reactor (GA) for N-Nbar search experimentAnnular core TRIGA reactor (GA) for N-Nbar search experiment

Economic solution for n-nbar:annular core TRIGA reactor 3.4 MWwith convective cooling, vertical channel, and large cold LD2 moderator (Tn ~ 35K). Unperturbed thermal flux in the vertical channel ~ 21013 n/cm2/s

Courtesy of W. Whittemore (General Atomics)

~ 1 ft

• GA built ~ 70 TRIGA reactors 0.0114 MW (th)• 19 TRIGA reactors are presently operating in US (last commissioned in 1992)• 25 TRIGA reactors operating abroad (last commissioned in 2005)• some have annular core and vertical channel• most steady, some can be pulsed up to 22 GW• safe ~ 20% EU uranium-zirconium hydride fuel

New development enhancing n-nbar search sensitivityNew development enhancing n-nbar search sensitivity

Very Cold Neutron Source with Tn ~ 2.2K

(IPNS/ANL R&D project by J.M. Carpenter et al., 2005)

J.M. Carpenter et al., 2005

2.2K Maxwellian

Method Present limit Possible future limit Possible sensitivity

increase factor

Intranuclear (N-decay expts)

7.21031 yr = 1unit Soudan II

7.51032 yr (Super-K) 4.81032 yr (SNO)

11

Geo-chemical (ORNL)

none 41081109 s (Tc in Sn ore)

20 100

UCN trap (6107 ucn/sec)

none ~ 1109 s 100

Cold horizontal beam

8.6107 s = 1unit @ILL/Grenoble

3109 s @HFIR/ORNL Not available

103

Cold Vertical beam

none 3109 – 11010 s

(SNOLAB) 103 104

ySensitivitSearch nn

Soudan-II limit Soudan-II limit ILL/Grenoble limit = 1 unit of sensitivity ILL/Grenoble limit = 1 unit of sensitivity

TRIGA Cold Vertical Beam, 3 years

Col

d B

eam

TRIGA Very Cold Vertical Beam, 3 years

Science impact of n-nbar searchScience impact of n-nbar search

If discovered:

• nnbar will establish a new force of nature and a new phenomenon leading to the physics at the energy scale of ~ 105 GeV • will provide an essential contribution to the understanding of BAU

• might be the first detected manifestation of extra dimensions and low QG scale

• new symmetry principles can be experimentally established: (BL)0

If NOT discovered:

• within the reach of improved experimental sensitivity will set a new limit on the stability of matter exceeding sensitivity of X-large nucleon decay experiments

• wide class of SUSY-based models will be removed (K. Babu and R. Mohapatra, 2001)

• further experiments with free neutrons will allow high-sensitivity testing

antimatter andmatter baryonic of eequivalenc nalgravitatio

10mm with theorem) (CPT whether 23

nn mm (L. Okun et al, 1984)

(S. Lamoreaux et al, 1991)

Vertical shaft ~ 1 km deep, with dia Vertical shaft ~ 1 km deep, with dia 5 m to be instrumented 5 m to be instrumented

Construction access from the top and the bottom of the shaftConstruction access from the top and the bottom of the shaft

Site isolated from the main underground lab Site isolated from the main underground lab

Heat removal of 3.5 MW TRIGA reactor (at the surface)Heat removal of 3.5 MW TRIGA reactor (at the surface)

Cryogen equipment for cold moderator (at the surface) Cryogen equipment for cold moderator (at the surface)

Many other things (too early to discuss) Many other things (too early to discuss)

What is required for experiment at SNOLAB?What is required for experiment at SNOLAB?

• • Vertical shafts and Lab infrastructure exists Vertical shafts and Lab infrastructure exists

• • International scientific community exists International scientific community exists (Program Advisory Committee, reviews, etc)(Program Advisory Committee, reviews, etc)

• • It might be possible to license a new reactor It might be possible to license a new reactor in Canada in Canada

Why at SNOLAB ?Why at SNOLAB ?