# Presentation: 523928

## Future Measurement of sin2213 at Nuclear Reactors

- Jonathan Link
- Columbia University
- June 6, 2003

- ′03

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Introduction

- Ue3 is important because it sets the scale for CP violation in the lepton sector.
- m132 is known from atmospheric (m132=m232+m122≈m232)
- If know your neutrino energy you know where to put your detector to optimize oscillations.

**<0.12 **(CHOOZ & Palo Verde)

- Atmospheric

- Solar

- Sin2213 can be investigated with Accelerators and/or with Reactors

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Methods of Measuring sin22

-  Measure with an Accelerator
- (JHF-SK and NuMI Off-axis)
- Appearance νμ→νe  (or νμ→νe with separate running)
- Off-axis to have a monochromatic νμ beam
- Long Baseline (300 – 900 km)
- Very large detector
-  sin2213 is not independently
- measured − parameter degeneracy
- (CPV phase , matter effects and mass hierarchy)

- sin2213

- ~sin

- ~cos

- Mass hierarchy and matter effects

- See talks by H. Minakata, H. Sugiyama and W. Winter in WG1

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Methods of Measuring sin22(Continued)

-  Measure at a Nuclear Reactor
-      (Previous experiments CHOOZ and Palo Verde)
- Baseline ~1 km
- Disappearance νe→νe
- Use identical near detector to measure reactor flux, spectrum and detector efficiency to cancel most systematics
- Look for small rate deviation from 1/r2 in a large reactor signal
- Direct measurement of sin2213

- Combining measurements from these two methods results in the best sensitivity to sin2213 and 

- See P. Huber WG1 today at16:30

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Nuclear Reactors as a Neutrino Source

-  Each fission liberates about 200 MeV of energy and generates about 6 neutrinos.  So for a typical commercial  reactor (3 GW thermal energy)
-   3 GW ≈ 2×1021 MeV/s → 6×1020 e/s

- Arbitrary

- Flux

- Cross Section

- Observable  Spectrum

-  The observable  spectrum is the product of the flux and the cross section.
-  The reaction process is inverse  decay:
**Two part coincident signal**
-  The spectrum peaks at ~3.7 MeV.

- e* p**→ e****+****n*
-                     *n Gd → *’s (8 MeV)

- ~30 s later

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## CHOOZ

-  Homogeneous detector
-  5 ton, Gd loaded, scintillating target
-  300 meters water equiv. shielding
-  2 reactors: 8.5 GWthermal
-  Used new reactors → reactor off data for background measurement
-  Baselines 1115 m and 998 m
-  Expected rate of  ~25 evts/day (assuming no oscillations)

- Chooz Nuclear Reactors, France

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Palo Verde

-  32 mwe shielding  (Shallow!)
-  Segmented detector:
- Better at handling the cosmic rate of a shallow site
-  12 ton, Gd loaded, scintillating target
-  3 reactors: 11.6 GWthermal
-  No reactor off running
-  Baselines 890 m and 750 m
-  Expected rate of ~50 evts/day (assuming no oscillations)

- Palo Verde Generating Station, AZ

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## CHOOZ and Palo Verde Results

-  Neither experiments found evidence for e oscillation.
-  This null result eliminated →e as the primary mechanism for the Super-K atmospheric deficit.

-  sin2213< 0.12 at 90% CL
-  Future experiments should try to improve on these limits by *at least* an order of magnitude.
- Down to sin2213<0.01
- In other words, a 1% measurement is needed!

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Sensitivity Reach as a Function of Exposure 

**90%CL ****at ****Δ****m****2**** = 3×10****-3**** eV****2**

- Assumes negligible background;    σcal   relative near/far energy calibration
-                                                         σnorm relative near/far flux normalization

*Huber et al hep-ph/0303232*

**Statistical error only**

**Fit uses spectral shape only**

**Exposure (ton GW****th**** year)**

**sin****2****2****θ****13**** Sensitivity**

- Speaking at 16:30 today.  Also W. Winter on Saturday at 17:00

- 400

- 8000

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Krasnoyarsk, Russia (hep-ex/0211070)

**115m**

**1000m**

- Completely underground facility was used by the Soviets for weapons production.

-  One ~2 GW reactor
-  Two 50 ton detectors
-  Near detector at 115 meters
-  Far detector at 1000 meters
-  About 60 days of reactor off running per year.
-  ~100 GW·tons
-    (4 years → ~0.02)

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Kashiwazaki, Japan (hep-ph/0211111)

**near**

**near**

**far**

-  7 Reactors, 24 GWthermal (most powerful site in the world)
-  Three ~8 ton detectors
-  Two near detectors at baselines of  300 to 350 meters
-  One far detector at ~1300 meters
-  ~190 GW·tons

- See O. Yasuda in WG1 today at 16:00

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Possible U.S. Sites

- Top 30 U.S. Sites by Power Performance

-  Most U.S. sites have one or two reactors.
-  One and two reactor sites are conceptually easier: only one baseline. (The experiment *can* be done at multi-reactor sites.)
-  U.S. two reactor sites are among the best in the world in power performance.
-    ~350 GW·tons (with a 50 ton detector)
-  Many U.S. sites have other favorable qualities such as potential for shielding.
- The challenge will be getting reactor operators to agree to work with us!

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## What is the Right Way to Make the Measurement?

- Start with the Systematics and Work Backwards...

- CHOOZ Systematic Errors, Normalization

- Near Detector
- Identical Near and Far Detectors
- Movable Detectors
-  Veto and Neutron Shield

- CHOOZ Background Error
- BG rate                                        0.9%

- Statistics may also be a limiting factor to the sensitivity.

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Movable Detector Scenario

- The far detector spends about 10% of the run at the near site where the relative efficiency of the two detectors is measured head-to-head.
- The detectors must be well underground to reduce the cosmic rate.
- So the near and far sites need to be connected by a tunnel!

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Detector Design

- Detector

- Tunnel Wall

- Larger version of CHOOZ (smaller KamLAND)
-  Homogenous Volume
-  Viewed by PMT’s
-  Gadolinium Loaded, Liquid Scintillator Target
-  Pure Mineral Oil Buffer
- In the Movable Scenario
-  Rail System for Easy Transport
-  Carries Electronics and Front-end DAQ.

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Systematic Error from Backgrounds

- At sites with more than one reactor there is no reactor off running, so other ways of measuring the backgrounds are needed.
- The toughest background comes from fast neutrons created by cosmic ’s.  They can mimic the coincidence signal by striking a proton and then capturing.

- Build it deeper 		(hard to do!)
- Veto ’s and shield neutrons  (*effective depth*)
- Measure the recoil proton energy and extrapolate into the signal region.

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Detailed Optimization Studies

- Allowing the variation of:
-  reactor power
-  run time
-  detector size
-  reactor capacity factor

-  near and far baselines
-  background rate
-  background sensitivity

-  fixed or movable
-  fraction time for cross calibration
-  one or two reactor scenarios

- Sampling of Scenarios

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Conclusions and Prospects

-  The physics of sin2213 is interesting and important.
-  An international proto-collaboration has been formed to work towards a proposal by 2005 (and a white paper this fall).
-  The search for a suitable reactor site is underway.

-  Controlling the systematic errors is the key to making this measurement.
-  Reactor sensitivities are comparable off-axis and the two methods are complementary.
-  With a 3 year run, the sensitivity in sin2213 could reach 0.01 (90% CL) at m2 = 2.5×10-3.

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Institutions of the Proto-Collaboration

- We are open to
-       new collaborators...

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Conclusions and Prospects

-  The physics of sin2213 is interesting and important.
-  An international proto-collaboration has been formed to work towards a proposal by 2005 (and a white paper this fall).
- The search for a suitable reactor site is underway.

-  Controlling the systematic errors is the key to making this measurement.
-  Reactor sensitivities are comparable off-axis and the two methods are complementary.
-  With a 3 year run, the sensitivity in sin2213 could reach 0.01 (90% CL) at m2 = 2.5×10-3.

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Question Slides

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Optimal Baseline

- At m2 = 2.5×10-3 the optimal region is quite wide.  In a configuration with a tunnel connecting the two detector sites, one should choose a far baseline that gives the shortest tunnel (~1200 meters).

- One must consider both the location of the oscillation maximum and statistics loss due to 1/r2.

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Reactor Sites Around the World

- Multi-Reactor Sites

- Under Consideration

- Former Host Site

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Experiment Timeline

- 2003

- 2004

- 2005

- 2006

- 2007

- 2008

- 2009

**Site Selection**

- 2010

**Run**

- 2011

**Proposal**

**Construction**

- Years

- 1 year	    11⁄2 years            2 years                     3 years (initially)

- Site Selection:  Currently underway.
- Proposal Phase:  Secure funding from government agencies
- (NSF and DOE)
- Construction Phase:  Tunnel construction and detector assembly
- Run Phase:  Initially planned as a three year run.  Results or
- events may motivate a longer run.

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Significant Contributions to the Sensitivity

-  Statistics in the far detector
-  Uncertainty in the relative efficiency of the near and far detector
- where *f* is the fraction of run time used for cross calibration
-  Uncertainty in the background rate in the far detector

- (with movable detectors)

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003

## Byron, Illinois

- The near detector could be placed as far back as 400 meters, but ***nearer is significantly better***.

- A Possible Site Configuration

- Surface access is beyond existing infrastructure.

- Jonathan Link, Columbia U.                                  NuFact03

- 6/6/2003