First results from T2K's upgraded near detector

First results from T2K's upgraded near detector XXI International Workshop on Neutrino Telescopes 2/10/2025 Gioele Reina (he/him) for the T2K collaboration JGU Mainz University [email protected] 2 Gioele Reina - First results from T2K’s upgraded near detector The T2K experiment Tokai 2 Kamioka Off-axis 2.5° Far Detector: Super-K Off-axis 2.5° Near Detector: ND280 Beamline, Target and Decay Volume 295 km 2.5° off-axis beam peaks at 600 MeV Related talks: S. King, L. Machado, E.Sandford Long-baseline (anti-)neutrino oscillation experiment Measure νμ disappearance and νe appearance to estimate neutrino oscillation parameters: δCP, θ23, Δm23, θ13 2 DOI:https://doi.org/10.1103/PhysRevD.88.032002 3 Gioele Reina - First results from T2K’s upgraded near detector ND280 and its Upgrade 4 Gioele Reina - First results from T2K’s upgraded near detector ND280 Near Detector Motivation ND280 needed to constrain flux and cross section reducing systematic uncertainties Total uncertainty on 1 Ring νμ reduced from 16.7% to 3.4% after ND constraints ND280 legacy limitations: ●Systematic uncertainties too large for T2K-II phase ●Low high-angle acceptance ●High proton detection threshold Limitations have been overcome by ND280 Upgrade SK 1 Ring νμ sample energy spectrum before and after ND fit arXiv:2303.03222 5 Gioele Reina - First results from T2K’s upgraded near detector ND280 Upgrade Replacement of 𝝅0 detector with three new subdetectors: ●Super Fine-Grained-Detector (SuperFGD) ●2 High Angle TPCs (HA-TPCs) ●6 Time of Flight planes (ToF) arXiv:1901.03750 6 Gioele Reina - First results from T2K’s upgraded near detector ND280 Upgrade Detectors SuperFGD (new active target): ●~2 million 1 cm3 scintillator cubes ●3 WLS fibres crossing each cube ●SiPMs readout at one end of each fibre ●PID improvement ●Low energy threshold ●Neutron reconstruction HA-TPCs: ●Argon-based gaseous mix ●Encapsulated Resistive Anode Micromegas (ERAMs) readout ●Better spatial resolution ●High angle track reconstruction ●Full angular coverage ToF: ●6 plastic scintillator planes ●20 bars for each plane ●SiPMs readout at both ends of each bar ●~175 ps time resolution ●In/out going particle identification Related talks: S. Levorato, M. Feltre, W. Okinaga 7 Gioele Reina - First results from T2K’s upgraded near detector ND280 Upgrade Improvements ●Lower proton detection threshold ●Higher detection efficiencies ●Higher angular acceptance ●Neutron kinematics via time of flight Neutron detection and reconstruction Proton detection threshold Muon angular detection efficiency before and after the upgrade High angle acceptance before (left) and after (right) upgrade arXiv:1901.03750, arXiv:2108.11779, arXiv:1912.01511, arXiv:1901.03750 protons, ND280 legacy Before Upgrade After Upgrade 8 Gioele Reina - First results from T2K’s upgraded near detector T2K runs with ND280 Upgrade ●Runs with partial upgrade in Dec. 2023 and March 2024 ●Upgrade installation completed in May 2024 ●5.2×1020 Protons on Target (POT) with upgrade ●Total since 2010: 4.62×1021 POT ●Beam power increased to 830 kW (planned to reach 1.3 MW) Full upgrade 9 Gioele Reina - First results from T2K’s upgraded near detector Preliminary Performances 16 Gioele Reina - First results from T2K’s upgraded near detector νeCC Selection ●Purity of 77.7% for track-like and 80.6% for shower-like events ●Boosted Decision Tree (BDT) for Shower identification and separation of e± from gamma background Electron/shower energy in νeCC, including purity Typical νeCC candidate event EM-shower 17 Gioele Reina - First results from T2K’s upgraded near detector νμCC0πNn Selection ●BDT for neutron selection ●Event level selection requiring at least one primary neutron in the event ●Purity of 67% at BDT cut 0.3 Typical νμCC0πNn candidate event Number of neutron candidates in νμCC0πNn, including purity BDT cut 0.3 T2K work in progress T2K work in progress Related talk: A. Srivastava Isolated neutron candidate 18 Gioele Reina - First results from T2K’s upgraded near detector Summary ●Full ND280Upgrade since summer 2024 ●Successful runs of neutrino beam ●First detector results and performances with the upgrade ●Reconstruction tuning ●Development of sample selection and systematics ongoing ●Exciting measurements are coming! Stay tuned! 19 Gioele Reina - First results from T2K’s upgraded near detector Backup 20 Gioele Reina - First results from T2K’s upgraded near detector Super-Kamiokande Far Detector ●T2K Far Detector ●Atmospheric neutrinos ●Superonva neutrinos ●Proton decay ●Cherenkov detector ●50 kton of ultra-pure water ●Gd doped for neutron tagging 21 Gioele Reina - First results from T2K’s upgraded near detector The Near Detectors INGRID ●On-axis ●Beam profile and flux direction monitoring ●Contrain flux systematics WAGASCI-BabyMIND ●1.5° off-axis ●Cross sections ν-H2O, ν-CH, & ν-Fe ●Cross section ration scintillator-water ND280 ●2.5° off-axis ●Cross-section and flux ●Oscillation analysis input 22 Gioele Reina - First results from T2K’s upgraded near detector Markov-Chain Time Calibration Method Matched hits: highly correlated hits for any granular detector: ●Each matching hit pair will have two channels (α, β), two times (t1, t2) and two distances (d1, d2). ●Measured difference: Δt = t1-t2 ●Expected difference: Δd = (d1-d2)/v, with v speed of light in the fibre ti tj ti tj Iteration N Iteration 0 Goal: minimize Δ = Δt-Δd with an iterative procedure 1. For each channel α evaluate average Δα = ∑βΔαβ/N 2. Δα is the offset correction for channel α 3. Apply correction at the next iteration tk+1 = tk+Δα 4. Repeat until convergence Equivalent to convergence of a row-stochastic matrix (Markov matrix) Given T(k) vector of channel offset residual, T(0) actual offsets, and M being a Markov-matrix It is possible to show 23 Gioele Reina - First results from T2K’s upgraded near detector Time Calibration for SuperFGD and ToF SuperFGD results before and after the calibration ToF results before and after the calibration 24 Gioele Reina - First results from T2K’s upgraded near detector HA-TPCs clustering reconstruction ●For poin-like deposit: radial spreading around the point ●For track-like deposit: perpendicular spreading around the track ●Grouping pads’ signals into clusters perpendicular to the track ●At 30° and 60° change of clustering Vertical clustering Diagonal clustering Horizontal clustering 25 Gioele Reina - First results from T2K’s upgraded near detector HA-TPCs dE/dx reconstruction Clustering not very efficient for diagonal tracks Modeling charge diffusion in the gas and charge spreading in the resistive layer This gives ratio between amplitude and charge for each pad creating a lookup table For each track look at the table and get the dE/dx by summing the all the charges