Yuri Kamyshkov/ University of Yuri Kamyshkov/ University of TennesseeTennessee

email: kamyshkov@utk.edu email: kamyshkov@utk.edu

DUSEL Theory Workshop, OSU April DUSEL Theory Workshop, OSU April 4, 20084, 2008

810 sec (in vacuum)N N à

Sensitivity for free neutron search (observation probability)

2obs

nN N

tP N

Sensitivity for bound neutron search (in nucleon decay expts)

exp

obsn

nucl

tP N

2 with "nuclear suppression factor"nucl N NR R

known from nuclear theory23 10.5 10 s R

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 free neutron N-Nbar search experiment Previous free neutron N-Nbar search experiment

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

80.86 10 secN N

= reference unit of sensitivity

Previous bound neutron N-Nbar search experiments Previous bound neutron N-Nbar search experiments Previous bound neutron N-Nbar search experiments Previous bound neutron N-Nbar search experiments

Experiment Year A nyear (1032) Det. eff. Candid. Bkgr. nucl , yr

Kamiokande 1986 O 3.0 33% 0 0.9/yr 0.431032

Frejus 1990 Fe 5.0 30% 0 4 0.651032

Soudan-2 2002 Fe 21.9 18% 5 4.5 0.721032

Super-K* 2007 O 245.4 10.4% 20 21.3 1.81032

Observed improvement weaker than SQRT is due to irreducible background of atmospheric neutrinos

*Preliminary S-K result

2nucl N NR

Important to know theoretical uncertainty

Important to know theoretical uncertainty e.g. intranuclear

nn pions with presumably large uncertainty is not accounted

e.g. intranuclear nn pions with presumably large uncertainty is not accounted

intranuclear searchexperiments Free neutron

search limit

#5; 5137#5; 5137YatesYates RossRoss

Nuclear reactoras a source of neutrons

1.5 km vacuum flight tube

Anti-neutrondetector

NNbar unique for DUSELNNbar unique for DUSEL

Shaft #5 might not be usable

3.4 MW annular coreresearch TRIGA reactor with Liquid D2 cold neutron moderator

TRIGA =TrainingResearchIsotopesfrom General Atomics

Control Room & Electronics

Detector Hall

Neutron Dump

Neutron shaft

Access Tunnel

Door

and not Horizontal and existing high-power reactors?

First, one needs RESEARCH not POWER reactor since by design virtue neutron fluxes are higher in former

Second, most important reason: vertical gravity produces devastating effect on the cold horizontal neutron beam vertical layout doesn’t suffer from this effect, thus 3.5 MW TRIGA is more efficient that largest 100 MW research reactor HFIR at ORNL

There are no research reactors with the cold beam available; they are all occupied by “fundamental” material research

Vertical flight path 1 km

Shaft diameter 15-20 ft

Vacuum chamber with 105 Pa

Active + passive magnetic shield 1 nT

Annular core TRIGA reactor 3.4 MWLD2 cryogenic cold moderator; neutron temperature 35K

Running time 3-5 years

Robust detection signature nA several pions 1.8 GeV

Annihilation properties are well modeled LEAR physics

Active magnetic shielding allows effect ON/OFF

Sensitivity increase more than 1000

Expected background at max sensitivity <0.01 event

Conservative DUSELbaseline configurationbased on establishedtechnologies

Possible improvement by on-going developments

Most exciting for experiment is a possibility of increasing sensitivity by large factor 1,000 (or nucl 1035 years)

Most exciting for experiment is a possibility of increasing sensitivity by large factor 1,000 (or nucl 1035 years)

(a) Larger shaft length

(b) Larger reactor power

(c) New reflector quality (developments at KEK/Japan)

(d) New “colder” moderator thermalizing neutrons to lower temperatures

Thermalization of n to the temperatures lower that 35Kis a challenge for CM theory;

non-sufficient R&D efforts

H.

Shi

miz

u, K

EK

/Jap

an

Economically possible in future

Can NNbar create a background for other DUSEL experiments?

Neutrinos ? For reactor located at the distance 2 km from the DUSEL main campus reactor antineutrino flux is not larger (e.g. by scaling from KamLAND) than solar neutrino flux

Might be still essential for CC antineutrino detection experiments at DUSEL (e.g. geo-neutrinos)

Thermal neutrons? can be easily shielded down to the environmental level. The environmental thermal neutron level is not precisely knownat Homestake mine ongoing R&Dto measure it and then we will have to make sure that TRIGA reactor will not increase this level.

Attenuation of thermal neutron flux by concrete shield

North Carolina State University: A.I. Hawari, B.W. Wehring, A. Young

Indiana University: W.M. Snow, C. M. Lavelle

University of Tennessee: W. Bugg, H.L. Dodds, Y. Efremenko, G. Greene, Y. Kamyshkov, S. Pfiffner

California State University at Dominguez Hills: K. Ganezer, J. Hill

Oak Ridge National Laboratory: G. Flanagan, J.O. Johnson, K. Williams

Los Alamos National Laboratory: T. Haines, A. Saunders

National Institute of Standards and Technology: Pieter Mumm

CNA Consulting Engineers: L. Petersen

International Collaborators: KEK, PNPI, Dubna, ILL, Swiss Neutronics

The group has experience and expertise in large projects construction (L3 /LEP Hadron Calorimeter, KamLAND) participation in large underground experiments (UT, CSUDH) large scale underground construction (CNA Engineering: MINOS,S1) reactor licensing, commissioning, operations (NCSU and ORNL) cold neutron sources and cold neutron experiments (IU, NCSU, UT) neutron technologies like supermirrors and mag. shield (IU, UT) neutron transport simulations (NCSU, ORNL, UT) intranuclear NNbar transition search (CSUDH) particle detector design, construction, simulations, cost estimate, etc.

construction feasibility

conceptual design

prelimdesign

boardapprove

construction

2009 2011 2013 2015

decision like CD0is needed

Vertical experiments at DUSEL are non-traditional “other uses”. Unique feature of DUSEL among other underground labs.

Homestake PAC received in 2005 following “vertical” LOIs:

#7 Search for neutron to antineutron transitions (Yu. Kamyshkov/UT)

#23 Study of diurnal Earth rotation (W. Roggenthen / SDSMT)

#33 Physics of cloud formation (J. Helsdon / SDSMT)

New Vertical LOIs (2007):

# Cold atom interferometry for detection of gravitational waves (M. Kasevich / Stanford U)

# Search for transitions to mirror matter (n n) Mirror matter is an alternative explanation of the dark matter (A. Serebrov / PNPI)