# Presentation: 376093

## Determining the Neutrino Mixing Angle 13 at Daya Bay

- Steve Kettell
- BNL

- Motivation
- Reactor anti-e
- Collaboration/BNL involvement
- Daya Bay Experiment

## Neutrinos

*Connecting Quarks to the Cosmos*: One of the eleven `profound questions’ addresses the mass and mixing of neutrinos. (2003)
*Quantum Universe*: “Detailed studies of the properties of neutrinos  their masses, how they mix, and whether they are Majorana particles will tell us whether neutrinos conform to the patterns of ordinary matter or whether they are leading us to the discovery of new phenomena.”
-      (2004)

- Daya Bay Experiment

- Kam-Biu Luk

## Recommendations of APS  Study Group (11/04) 

- on fast track

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## Recommendations from NuSAG (3/06)

*A reactor experiment is valuable regardless of its timing with respect to an accelerator experiment.*

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## Recommendations from NuSAG (2)

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## Neutrino Mixing 

**Majorana phases**

**Six parameters: 2 ********m****2****, 3 angles, 1 phase**** ****+ 2 Majorana phases**

- Pontecorvo-Maki-
- Nakagawa-Sakata Matrix

-  For three generations of massive neutrino, the weak eigenstates are
-    not the same as the mass eigenstates:

- solar                  reactor                          atmospheric neutrinoless
- reactor           accelerator LBL           accelerator LBL     double- decay

-  PMNS matrix parameterization:

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## Neutrino Oscillation 

-    The probability of e appearance is given by:

-    The probability of eX disappearance is:

******m****2****32 ****=(2.4****+0.4****-0.3****)********10****-3 ****eV****2**
**   ********23 ******** 45******** **
******m****2****21 ****=(7.8****+0.6****-0.5****)********10****-5**** eV****2**
**   ********12 ****=(32****+4****-3****)******

- m231  m232 >> m221
- 12 and 23 are large

**Unknowns: ****sin****2****2********13****, ********,  sign of ********m****2****32**

- Complementary

- +

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- Kam-Biu Luk

## Current Knowledge of 13

**Current Knowledge of ********13**

- 2.7%, 6%  _without_ near detectors

- 

- 
- m

- allowed region

-  limited statistics
-  reactor-related systematic errors:
-      - energy spectrum of e (~2%)
-      - time variation of fuel composition (~1%)
-  detector-related systematic error (1-2%)
-  background-related error (1-2%)

**Established technique**
****** ****with improvements**

- Limit on  from Chooz

- Daya Bay Experiment

- Kam-Biu Luk

## Detection of antineutrinos in liquid scintillator

-  Time- and energy-tagged signal is a good
-     tool to suppress background events.

-  Energy of e is given by:

- E  Te+ + Tn + (mn - mp) + m e+  Te+ + 1.8 MeV

- 10-40 keV

-   The reaction is the inverse ****-decay in Gd-doped liquid scintillator:

**Detection of antineutrinos in liquid scintillator**

- 50,000b

-      0.3b

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## How To Reach A Precision of 0.01 ?

**Powerful nuclear power plant ****	****(11.6********17.4 GW****th****)**
**Large detectors to reduce statistical error (4********20 tons)**
**100-150k events/year at the far detector (2-3 years for 0.2%)**
**Near and far detectors to minimize reactor-related errors (2+1)**
**Optimize baseline to maximize sensitivity and further reduce any residual reactor-related errors**
**Identical detectors to reduce detector-related systematic error**
**Interchange near and far detectors to further reduce the detector systematic uncertainty**
**Sufficient overburden and shielding to reduce background**
**Comprehensive calibration to reduce detector systematic error**

- Daya Bay Experiment

- Kam-Biu Luk

## Location of Daya Bay

**55 km**

**45 km**

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## Total length: ~3200 m

**Daya Bay**
**NPP**

**Ling Ao**
**NPP**

**Daya Bay Near**
**360 m from Daya Bay**
**Overburden: 97 m**** **

**Far site**
**1600 m from Lingao**
**1900 m from Daya**
**Overburden: 350 m **

**Ling Ao-ll NPP**
**(under const.)**

**8% slope**

**672 m**
**(12% slope)**

**Ling Ao Near**
**500 m from Lingao**
**Overburden: 98 m **

**Mid site**
**~1000 m from Daya**
**Overburden: 208 m **

**Entrance portal**

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## The Site

**LingAo II NPP:**
**2 ******** 2.9 GW****th**
**Ready by 2010**** **

**The Site**

**Daya Bay NPP:**
**2 ******** 2.9 GW****th**** **

**LingAo NPP:**
**2 ******** 2.9 GW****th**** **

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- Kam-Biu Luk

## The Daya Bay Collaboration

- X. Guo, N. Wang, R. Wang
*Beijing Normal University, Beijing 100875, China*
- L. Hou, B. Xing, Z. Zhou
*China Institute of Atomic Energy, Beijing 102413, China*
- M.C. Chu, W.K. Ngai
*Chinese University of Hong Kong, Hong Kong, China*
- J. Cao, H. Chen, J. Fu, J. Li, X. Li, Y. Lu, Y. Ma, X. Meng, R. Wang, Y. Wang, Z. Wang, Z. Xing,
- C. Yang, Z. Yao, J. Zhang, Z. Zhang, H. Zhuang, M. Guan, J. Liu, H. Lu, Y. Sun, Z. Wang, L. Wen,
- L. Zhan, W. Zhong
*Institute of High Energy Physics, Beijing 100039, China*
- X. Li, Y. Xu, S. Jiang
*Nankai University, Tianjin 300071, China*
- y. Chen, H. Niu, L. Niu
*Shenzhen University, Shenzhen 518060, China*
- S. Chen, Q. Su
*Tsinghua University, Beijing 100084, China*
- K.S. Cheng, J.K.C. Leung, C.S.J. Pun, T. Kwok, H.H.C. Wong, R.H.M. Tsang
*University of Hong Kong, Hong Kong, China*
- H. Liang, G. Jin, J. Wang, Q. Wang, X. Yu, Y. Zhou
*University of Science and Technology of China, Hefei 230026, China*
- Z. Li, C. Zhou
*Zhongshan University, Guangzhou 510275, China*
- B.Y. Hsiung
*National Taiwan University, Taipei, Taiwan, Republic of China*

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## The Daya Bay Collaboration (cont.)

- Yu. Gornushkin, I. Nemchenok, A. Olchevski, E. Yakushev
*Joint Institute of Nuclear Research, Dubna, Russia*
- V.I. Aleshin, Yu.V. Gaponov, V.I. Kopeikin, V.P. Martemyanov, L.A. Mikaelyan, V.G. Tarasenkov,
- V.N. Vyrodov
*Kurchatov Institute, Moscow, Russia*
**M. Bishai, M. Diwan, D. Jaffe, J. Frank, A. Garnov, R. Hahn, S. Kettell, L. Littenberg, K. Li, B. Viren, M. Yeh**
**Brookhaven National Laboratory, Upton, NY 11973-5000, USA**
- R.D. McKeown, C. Mauger, C. Jillings
*California Institute of Technology, Pasadena, CA 91125, USA*
- B.L. Young, K. Whisnant
*Iowa State University, Ames, Iowa 50011, USA*
- W. Edwards, K. Heeger, K.B. Luk
*University of California and Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA*
- V. Ghazikhanian, H.Z. Huang, S. Trentalange, C. Whitten Jr.
*University of California, Los Angeles, CA 90095, USA*
- K. Lau, B.W. Mayes, L. Pinsky
*University of Houston, Houston, Texas 77204, USA*
- J.C. Peng
*University of Illinois, Urbana-Champaign, Illinois 61801, USA*

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## Why BNL?

- The Physics is compelling! and a critical step to CP
- BNL provides a strong National Laboratory presence that will make this experiment viable for the DOE.
- BNL has a rich and storied tradition in  physics: in both the Physics and Chemistry departments
- BNL Chemistry has been involved in liquid scintillator research for Daya Bay for 3 years
- This experiment provides a bridge from the current Physics Department effort on MINOS to a long-baseline effort to measure CP violation in the neutrino sector.

- Daya Bay Experiment

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## BNL involvement in Daya Bay

- Formally joined collaboration at Feb. 2006 meeting in Beijing
- Member of Institutional Board (Kettell)
- Lead of liquid scintillator task force (Hahn,Yeh)
- Lead of muon veto task force (Littenberg, Diwan, Bishai)
- Central detector task force (Kettell)
- Simulations task force (Jaffe)
- Project and other engineering resources available

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## Gd-loaded Liquid Scintillator

-  R&D effort at BNL:
-    - Gd (carboxylate ligands) in         PC and dodecane
-    - all stable for a year
-    - att. Length > 15m
-    - promising new scintillator: Linear Alkyl Benzene (LAB)

**Gd-loaded Liquid Scintillator**

- Significantly reduces backgrounds due to the short neutron capture time and high capture energy

**BNL has successfully loaded 1% Gd into 100% LAB**
**Gd-LAB has much better transparency at < 400 nm and at least ~50% improved optical transparency at 430 nm, compared to Gd-PC**

- Palo Verde

- Chooz

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## Conceptual Design of Detector Modules

**Three-layer structure: **
- I.   Target: Gd-loaded liquid scintillator
- II.  Gamma catcher: liquid scintillator, 45cm
- III. Buffer shielding: mineral oil, ~45cm
**  **
**Possibly with diffuse reflection at ends. For ~200 PMT’s around the barrel:**

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## Cross Section of Tunnel For Daya Bay Experiment

**Cross Section of Tunnel For Daya Bay Experiment**

- 1.2 m

- 1.2 m

- 7.2 m

- 0.8 m

- 3.2 m

- 3.2 m

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## Cosmic-ray Muon

**Cosmic-ray Muon**

-  Apply a modified Gaisser parameterization for cosmic-ray flux at surface
-  Use MUSIC and mountain profile to estimate muon flux & energy

|  | DYB | LingAo | Mid | Far |
| --- | --- | --- | --- | --- |
| Elevation (m) | 97 | 98 | 208 | 347 |
| (m.w.e.) | 280 | 280 | 560 | 930 |
| Flux (Hz/m2) | 1.2 | 0.94 | 0.17 | 0.045 |
| Mean Energy (GeV) | 55 | 55 | 97 | 136 |

- near site

- far site

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## Conceptual Design of Shield-Muon Veto

- Detector modules enclosed by 2m of water to shield neutrons (and gamma-rays)
- Water shield also serves as a Cherenkov veto
- Augmented with a muon tracker: scintillator or RPC's
- Combined efficiency of Cherenkov and tracker > 99.5%

**Neutron background vs. **
**thickness of water**

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- Kam-Biu Luk

## Background

|  | Near Site | Far Site |
| --- | --- | --- |
| Radioactivity  (Hz) | <50 | <50 |
| Accidental  B/S | <0.05% | <0.05% |
| Fast neutron background B/S | 0.15% | 0.1% |
| 8He/9Li B/S | 0.55% | 0.25% |

**Natural Radioactivity**: PMT glass, Rock, Radon in the air, etc
**Slow neutron, and fast neutron**
-        -  Neutrons produced in rock and water shield (99.5% veto efficiency)
**Cosmogenic isotopes: 8He/9Li which can ********-n decay**
-  -  Cross section measured at CERN (Hagner et. al.)
-  -   Can be measured in-situ, even for near detector with muon rate ~ 10 Hz.
**Use a modified Palo Verde Geant3 MC to model response of detector**

- The above numbers are before shower-muon cut.

- 20t module

- For reference, 560(80) neutrino events per detector per day at the near(far) site

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## Systematic Uncertainty

| Systematic error | Chooz | Daya Bay |
| --- | --- | --- |
| Reaction Cross Section | 1.9% |    0,  near-far cancellation |
| Energy released per fission | 0.6% |    0,  near-far cancellation |
| Reactor Power | 0.7% | 0.06%,  near-far cancellation |
| Number of Protons | 0.8% | 0,  detector swapping |
| Detection efficiency* | 1.5% | ~0.2%, fewer cuts, detector swapping |
| Total | 2.75% | ~0.2% |

- Statistical Error (3 years):     0.2%
-  Residual systematic error:  ~ 0.2%

- *
-   No Vertex cut.
-   Residual detection error is dominated by the **neutron energy cut** at 6 MeV
-    arises mainly from the energy-scale uncertainties. (It is ~0.2% for a 1%
-    energy-scale error at 6 MeV.)
** ****Positron energy cut** is negligible.

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##  Sensitivity of sin2213

- Daya Bay site
-    -  baseline = 360 m
-    -  target mass = 40 ton
-    -  B/S = ~0.5%
- LingAo site
-    -  baseline = 500 m
-    -  target mass = 40 ton
-    -  B/S = ~0.5%
- Far site
-    -  baseline = 1900 m to DYB cores
-                        1600 m to LA cores
-    -  target mass = 80 ton
-    -  B/S = ~0.2%
- Three-year run (0.2% statistical error)
- Detector residual error = 0.2%
- Use rate and spectral shape

- 90% confidence level

** ****Sensitivity of sin****2****2********13**

- 2 near + far

- near (40t) + mid (40 t)
- 1 year

- Daya Bay Experiment

- Kam-Biu Luk

## Summary and Prospects

- The Daya Bay nuclear power facility in China and the mountainous topology in the vicinity offer an excellent opportunity for carrying out a measurement of sin2213  at a sensitivity of 0.01.
- The Chinese funding agencies have agreed to a request of RMB 150 million to complete civil construction and ~half of the detector.
- NuSAG has endorsed US participation in a 13 experiment, HEPAP is evaluating 13 experiments as part of the Roadmap, and we await a decision by DOE.
- BNL/LBNL submitted R&D request to DOE for FY06 in January 2006.
- Will complete a conceptual design of detectors, tunnels and underground facilities in 2006, aiming for CD1 this year and CD2 in 2007.
- Plan to commission the Fast Deployment scheme in early FY2010, and
- 	Full Operation late in FY2010.

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## Backup

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## Tunnel construction

**The total tunnel length is ~3 km**
**Preliminary engineering design: Cost ~$3K/m**
**Construction time ~15-24  months**
**A similar tunnel exists on site as a reference**** **

- 7.2 m

- 7.2 m

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## Bore Drilling

**bursa**

**Bore Drilling**

| Location | Drill Depth (m) |
| --- | --- |
| ZK1 | 211 |
| ZK2 | 210 |
| Zk3 | 127 |
| Zk4 | 133 |

- Ongoing and will finish
- by the end of March.

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## Slide 30

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##  Prototype Detector at IHEP

** ****Prototype Detector at IHEP**

-  Constructing a 2-layer prototype with
-    0.5 t Gd-doped LS enclosed in 5 t of
-    mineral oil, and 45 8” PMT's to evaluate
-    design issues at IHEP, Beijing

**Steel tank**

**acrylic vessel**

**PMT mount**

**Front-end board (version 2)**

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##  The Aberdeen Tunnel Experiment

**Installing proptubes in Sept, 2005**

** ****The Aberdeen Tunnel Experiment**

-  Study cosmic muons & cosmogenic background in Aberdeen Tunnel, Hong Kong.

- similar geology
- between Aberdeen
- and Daya Bay

- Overburden ~
- Daya Bay sites

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## Management Structure

- The Collaboration approved bylaws (2/06).
- Institutional Board, consisting of one representative from each Member Institution and two spokespersons, established (2/06).
- Executive Board established (2/06):
- 	Y. Wang (China)			 A. Olshevski (Russia)
- 	C. Yang (China)			 K.B. Luk (US)
- 	M.C. Chu (Hong Kong)		 R. McKeown (US)
- 	Y. Hsiung (Taiwan)
- Scientific spokespersons are chosen:
- 	Y. Wang (China), K.B. Luk (US)
- Task forces on communication, antineutrino detector, muon veto,
-      liquid scintillator, simulation, and calibration set up. Each task
-      is led by at least one member from China and one from US.
- Begin to discuss the Construction Project management.

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## What Target Mass?

**Systematic error (per site):**
**    ****Black : 0.6%**
**      ****Red : 0.25%**
**     ****Blue : 0.12%**

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## Where To Place The Detectors ?

**Where To Place The Detectors ?**

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## Where To Place The Detectors At Daya Bay?

**Where To Place The Detectors At Daya Bay?**

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## A Versatile Site

** ****Rapid deployment:**
-  Daya near site + mid site
-  0.7% reactor systematic
-   error

** ****Full operation:**
-          (1) Two near sites + Far site
-          (2) Mid site + Far site
-          (3) Two near sites + Mid site + Far site
-       Internal checks, each with different
-       systematic

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## What Have We Learned From Chooz?

| CHOOZ Systematic Uncertainties |  |
| --- | --- |
| Reactor  flux & spectrum
Detector Acceptance | 2%
1.5% |
| Total | 2.7% |

- Rate:
-    ~5 events/day/t (full power)
-     including 0.2-0.4 bkg/day/t

- e + p  e+ + n
- e+ + e-  2 x 0.511 MeV 
- n + Gd  8 MeV of s;  ~ 30 s

- ~3000 e candidates
- (included 10% bkg) in
- 335 days

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## Reactor anti-e

**Reactor anti-********e**

- For 235U, for instance, an
- average of 6 es are produced per fission (~200 MeV).

- e/MeV/fission

**3 GW****th**** ****generates**** 6********10****20 ********e**** per sec**

- -42

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## Time Variation of Fuel Composition

- Typically known to ~1%

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## How To Measure 13 With Reactor e?

**How To Measure ********13**** With Reactor ********e****?**

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## Background

- Depends on the
- flux of cosmic
- muons in the
- vicinity of the
- detector

- Go as deep
- as possible!

- Keep everything as radioactively pure as possible!

- KamLAND

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## -n Decay Of 8He And 9Li

******-****n Decay Of ****8****He And ****9****Li**

- Correlated final state: β+n+2α

- Correlated final state: β+n+7Li

- τ1⁄2 = 178 ms 49.5% Correlated

- τ1⁄2 = 119 ms 16% Correlated

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## Background

|  | Near Site | Far Site |
| --- | --- | --- |
| Radioactivity  (Hz) | <50 | <50 |
| Accidental  B/S | <0.05% | <0.05% |
| Fast Neutron background B/S | 0.15% | 0.1% |
| 8He/9Li B/S | 0.55% | 0.25% |

- Use a modified Palo-Verde-Geant3-based MC to model response of detector.
- Cosmogenic isotopes: 8He/9Li which can -n decay
-  -   Cross section measured at CERN (Hagner et. al.)
-  -   Can be measured in-situ, even for near detector with muon rate ~ 10 Hz.

- The above number is before shower-muon cut
- which can further reduce cosmogenic background.

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## Background estimated by GEANT MC simulation

|  | Near  | far |
| --- | --- | --- |
| Neutrino signal rate(1/day) | 560 | 80 |
| Natural backgrounds(Hz) | 45.3 | 45.3 |
| Single neutron(1/day) | 24 | 2 |
| Accidental BKG/signal | 0.04% | 0.02% |
| Correlated fast neutron Bkg/signal  | 0.14% | 0.08% |
| 8He+9Li BKG/signal | 0.5% | 0.2% |

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## Calibration

- Radioactive Source
-          137Cs, 22Na, 60Co, 54Mn, 65Zn , 68Ge, Am-Be
-       252Cf, Am-Be
- Gamma generator
-       **p+****19****F→ ****α****+****16****O*+6.13MeV;       ****p+****11****B→ ****α****+****8****Be*+11.67MeV**
- Backgrounds
-      40K, 208Tl, cosmic-induced neutrons, Michel’s electrons, ...
- LED calibration

**KI & CIAE**

**Hong Kong**

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## Synergy of Reactor and Accelerator Experiments

**       ****Δ****m****2**** = 2.5****×****10****-3**** eV****2**** ****sin****2****2********13**** = 0.05**

- Reactor experiments can help in** **
- Resolving the 23 degeneracy
-   (Example: sin2223 = 0.95 ± 0.01)

- 90% CL

**McConnel & Shaevitz, hep-ex/0409028**

**90% CL**

**Reactor w 100t (3 yrs) +T2K**
** ****T2K (5yr,********-only) **
** ****Reactor w 10t (3 yrs)**
**+T2K**

- Reactor experiments provide
- a better determination of 13

- Daya Bay Experiment

- Kam-Biu Luk