1. 1 Work report (2013.09-2014.09) Haoqi Lu IHEP Neutrino group 2014.11.21 1

2. Outline – Resume – Daya Bay experiment Data analysis – Muon system paper – Work for INWG – Update fast neutron spectrum Water Cherenkov detector running – JUNO Multiple muon and Li9/He8 background study Top track MC and design Liquid scintillator with fiber option R&D Others 22

3. 3 Experiences – 2000.9-2004.7 Henan Normal University, Bachelor – 2004.9-2009.7 IHEP, PhD – 2009.7-2012.7 IHEP, Assistant researcher, DayaBay – 2012.7 -, Associate researcher, DayaBay Mainly work on veto system of DayaBay and JUNO. 2004-2009, Daya Bay veto detector design and prototype R&D; 2009-2010 ， work on DayaBay software, event generation and event mixing. 2010-, Level 3 of DayaBay Water Cherenkov detector, work for detector installation, hardware, software, commissioning and running. Resume

4. 4 1.1 Data analysis 4 1.1.1 Muon system paper Assist in writing the draft of Daya Bay veto system paper(The Muon System of the Daya Bay Reactor Antineutrino Experiment). Provides all the analysis plots of Water Cherenkov detector performance(10 plots). These plots include the study of event rate, PMT noise, detector efficiency, water attenuation length and so on. The muon system of the DayaBay Reactor Antineutrino Experiment,NIMA57063 1.1.2 Work for INWG(The Isotope and Neutron Wroking Group) – The convener of INWG. – The group would give the paper draft about spallation neutrons study at end of 2014. – Now, the work is going underway. 1. Daya Bay experiment

5. 1.1.3 Update of fast neutron spectrum The typical method is to extend the neutrino prompt signal energy range and use high energy range spectrum to estimate low energy spectrum. – It could have big systematic error for fast neutron spectrum estimation. Use different detectors (outer water veto detector and RPC detector) to obtain fast neutron spectrums to cross check with each other. – Get low energy range (0-12MeV) spectrum directly from data to reduce systematic error. 55

6. 1.2 Detector running ： A contact person of Water Cherenkov detector running. The main responsibility is to handle issues from detector running. 66 Trigger rate of three EHs IWS Muon efficiency( by AD muons) The water Cherenkov detector performance is good and running at a stable state from 2012.

7. 7 2. JUNO 2.1.1 Multiple muon study Multiple muon events can’t be neglect for underground large size detector(JUNO). Using a parameterization method to study the JUNO muon flux and multiple muon ratio. This study shows that the multiple muon ratio is about 20% at JUNO depth. Considering the detector geometry effect, the multiple muon ratio is 10% in detector. This result has been used to produce the JUNO muon generator for MC study. Multiple muon flux at different depth (vertical muon) Muon multiplicity ratio after detector simulation. JUNO depth

8. 8 2.1.2 Li9/He8 background estimation We know Li9/He8 is the main background in Daya bay. We are more concern about this background in huge size detector(JUNO). Two method for Li9/He8 estimation. Method 1:Use different experiments results for JUNO Li9/He8 yield constrain (57+/- 14/day); Method 2:Using Geant4 simulation and experiment data comparison to get the results (73.6/day). Two results are roughly consist with each other. We can use this result for Li9/He8 background subtraction and live time study. Method 1 Exp. Hall Rock Water Pool CD Muon Method 2 (MC)

9. Detector concept design 9 Li9/He8 is the main background of JUNO. We intend to use muon track for muon background reduction. The top tracker will focus on well study the cosmogenic background production and muon events calibration. 2.2 Top tracker MC and design 2.3 Liquid scintillator with fiber option R&D

10. 10 2.2.1 OPERA target tracker for JUNO OPERA scintillator from target tracker would be the baseline of JUNO top tracker. Muon and radioactive events spectrum(MC) Due to the high radioactivity from experiment hall rock, MC are needed for detector design. Preliminary study show that:  At least 3 super layers(x-y to form one super layer) will be needed.  2m distance between two adjacent super-layers. Due to the high radioactivity from experiment hall rock, MC are needed for detector design. Preliminary study show that:  At least 3 super layers(x-y to form one super layer) will be needed.  2m distance between two adjacent super-layers.

11. 2.2.2 Top tracker MC and design 4m*4m(two layer X-Y, 16 strip per layer) 4m*0.25m*0.04m(8 fiber per unit) The MC study shows:  This option can have a good capability for muon and radioactivity events discrimination;  High muon detect efficiency;  Need prototype R&D. 11 2.2.1 Liquid scintillator with fiber option Liquid scintillation with optical fiber detector was proposed as a selection for JUNO top tracker. The dimension of each unit is 4m*25m*4cm. There are 8 fibers in each cell with two layer structure of XY readout.

12. 12 2.3 Liquid scintillator with fiber option R&D Prototype:TiO2 doped PVC box, Dimension:100cm*25cm*12cm, 8 fiber in one box, Multi–anode PMT readout. Prototype:TiO2 doped PVC box, Dimension:100cm*25cm*12cm, 8 fiber in one box, Multi–anode PMT readout. PMT fiber

13. 13 Test results ： Experiment data shows that each PMT can received 30 photoelectron ; Muon detection efficiency of the module can reach 99.40%; Preliminary study shows that liquid scintillator with optical fiber detector can have a very good performance. Work with Jilei Xu. Detector performance PMT calibration: gain ~6*10e6 Muon spectrum

14. Concept Design Report(CDR) of JUNO – Assist in writing and finish the first chinese and english version of CDR (the veto detector part). JUNO simulation work group – Top tracker simulation convener Project archives ： – Contact person of JUNO veto detector part Talk: – Reactor-based neutrino experiments, Physics in collision, Beijing, Sep,2013 14

15. Publications DayaBay collaboration, Improved measurement of electron antineutrino disappearance at Daya Bay, Chinese Physics C37, 011001 (2013) ； Dayabay collaboration, Spectral Measurement of Electron Antineutrino Oscillation Amplitude and Frequency at Daya Bay, Phys. Rev. Lett. 112, 061801 (2014) The muon system of the Daya Bay Reactor Antineutrino Experiment, NIMA57063 15

16. 16 Thanks!