systematic errors of reactor neutrino experiments and ideas about new detectors
Download
Skip this Video
Download Presentation
Systematic errors of reactor neutrino experiments and ideas about new detectors

Loading in 2 Seconds...

play fullscreen
1 / 30

Systematic errors of reactor neutrino experiments and ideas about new detectors - PowerPoint PPT Presentation


  • 108 Views
  • Uploaded on

Systematic errors of reactor neutrino experiments and ideas about new detectors. Yifang Wang Institute of High Energy Physics, Beijing Nov.28, 2003. How big sin 2 2 q 13 is ?. J. Bahcall et al., hep-ph/0305159. M. Maltoni et al., hep-ph/0309130.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Systematic errors of reactor neutrino experiments and ideas about new detectors' - naida-mckenzie


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
systematic errors of reactor neutrino experiments and ideas about new detectors

Systematic errors of reactor neutrino experiments and ideas about new detectors

Yifang Wang

Institute of High Energy Physics, Beijing

Nov.28, 2003

how big sin 2 2 q 13 is
How big sin22q13 is ?

J. Bahcall et al., hep-ph/0305159

  • M. Maltoni et al., hep-ph/0309130

Sin22q13 ~ 3%, Chooz limit: Sin22q13 < 10%

summary about systematic errors
Summary about systematic errors
  • There are three main types of errors: reactor related(3%), background related(0.5-4%) and detector related(3%)
  • Use two detectors, far/near to cancel reactor related errors completely and some of detector/background related errors
  • Use movable detectors, near-far, to cancel all backgrounds and some of detector related errors
  • Sufficient shielding to reduce backgrounds

Can we do better than 1% ???

possible arrangement
Possible arrangement

500m

500m

1500m

1500m

Nf=P1500(A+B)/15002

Nn=P500(A+B)/5002

Reactor errors

canceled out exactly

another possibility
Another Possibility

1200m

300m

300m

1500m

1500m

Nf=P1500(A+B)/15002

NnA=P300(A)/3002 +P1237(B)/12372

NnB=P300(B)/3002 +P1237(A)/12372

Reactor errors:

~0.1% @ DA ~ 1.5%

kamland
KamLAND

1000t scintillators

Shielding:

3000 MWE/3m Water

180 km baseline

Signal: ~0.5/day

Eff. ~40%

BK:

corr.: ~0.001/day

uncorr. ~0.01/day

experience gained
Experience gained
  • Very good shielding
  • Balloon not good  target mass not well defined
  • Light transport in scintillator unknown  particularly bad for Large detectors  large error on position reconstruction
  • Background from 8He/9Li
  • Not good enough veto tracking system
  • 3m water shielding gives a neutron reduction of >13*106(high energy).
important point to have small systematic error
Important point to have small systematic error
  • Energy threshold less than 0.9 MeV
  • Homogeneous detector
  • Scintillator mass well determined
  • Target scintillator all from one batch, mixing procedures well controlled
  • Not too large detector
  • Comprehensive calibration program
  • Background well controlled  good shielding
  • Be able to measure everything(Veto ineff., background, energy/position bias, …)
  • A lot of unforeseen effects will occur when looking at 0.1% level
further reduce systematic errors multiple modules
Further reduce systematic errors: multiple modules
  • Many modules, 8t each, 100-200 8”PMT/module
  • 1-2 at near, 4-8 at far, small enough for movable calibration
  • Correlated error cancelled by far/near
  • Uncorrelated error can be reduced
  • Event rate:

near: ~500-2000/day/module

Far: ~40/day/module

  • 100 days calibration at the near pit

 0.2-0.5% statistical error

  • Two reference modules 100 days,

others ~ 10 days calibration

oil

Gd-scintillator

advantages with multiple modules
Advantages with multiple modules
  • Smaller modules have less unknowns
  • Multiple handling to control systematic error
  • Easy construction
  • Easy movable detector
  • Scalable
  • Easy to correct mistakes
structure of the module
Structure of the module

III

I

II

  • Three layers module structure

I. target: Gd-loaded scintillator

II. g-ray catcher: normal scintillator

III. Buffer shielding: oil

  • Advantages:
    • Well defined fiducial volume
    • No cut on position  small systematics
  • Disadvantages:
    • Complicated mechanical structure
    • Light yield matching/energy bias ?

Need careful MC study

slide21

position resolution

Cubic

Cylindrical

Position bias

cylinder with reflection
Cylinder with reflection

8MeV, Light yield 7000/MeV, QE=20%, QED1=60%,

Buffer=50cm, 100 8” PMT

background correlated
Background - correlated
  • Cosmic-muon-induced neutrons:
    • B/S < 0.005  1/day @ ~1km
    • Can be measured by veto tagging, accuracy<20%
    • Veto rate < 1KHz, 2-3 layers RPC(1600-2400 m2) ?
    • Methods:
      • Overburden > 100 MWE
      • Active Veto, ineff. < 0.5%, known <0.2%
    • Three scenarios:
other correlated backgrounds
Other correlated backgrounds
  • b-neutron instable isotopes from cosmic m
    • 8He/9Li, Br(n) = 12%/48%, 9Li dominant
    • Production rates = fm·NA ·s ·Br
    • Depth > 300 MWE, best 1000 MWE
background uncorrelated
Background - Uncorrelated
  • B/S < 0.05  < 8/day @ far site
  • Can be measured by swap method, precision ~ B/s=2.5%/day
  • single rate @ 0.9MeV < 50Hz

2· Rg · Rn· t < 0.04/day/module

  • Methods:
    • Low activity glass for PMT, > 0.5m oil shielding (dominant!)
    • 3 MWE shielding, low activity sand/aggregate or Fe ?
    • Rn concentration < 20 Bq/m3, N2 flushing ?
    • (U, Th, K) in Scintillator < 10-13 g/g, clean Gd
    • All mechanical structure made of low activity materials
    • Calibration gadget made of clean materials such as Teflon, …
    • Clean everywhere, no dust, no …
our estimate of systematic errors per module
Our estimate of systematic errors per module
  • Reactor < 0.1%
  • Background < 0.2%
  • Energy cut ~ 0.2%
  • Position cut ~ 0.2%
  • Time cut < 0.1%
  • Livetime ~ 0.1%
  • Other unexpected <0.2%
  • Total < 0.5%
r d efforts
R&D efforts
  • Low radioactive glass PMT
  • Low radioactive Gd-loaded liquid scintillator
    • Development
    • Mixing/purification
    • Monitor/Aging study
  • Mechanics of shielding structure
  • A lab for Low radioactive materials
  • Mass production of glass RPC
summary
Summary
  • Measuring Sin22q13 is a very important experiment, an unique opportunities for us
  • Systematic error can be controlled to ~0.5%.
  • Daya bay power plant is a good choice for the experiment
ad