Final Results from the MEG Experiment and the Status of MEG-II

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1 Final Results from the MEG Experiment and the Status of MEGII Francesco Renga INFN Roma HQL 2016 Virginia Tech, May

Charged Lepton Flavor Violation (clfv) Highlights Charge Lepton Flavor conservation in the Standard Model is an accidental symmetry, arising from the particle content of the

2 Charged Lepton Flavor Violation (clfv) Highlights Charge Lepton Flavor conservation in the Standard Model is an accidental symmetry, arising from the particle content of the model clfv almost unavoidable in most of New Physics models Charged LFV is THE signature for New Physics A. Scöhning SUSY predictions ~ Blackenburg, Isidori,JonesPerez 12 2

clfv and direct NP searches at the LHC clfv rates strongly depend on the details of the flavor structure of new physics: even within the same model, LFV constraints can be

3 clfv and direct NP searches at the LHC clfv rates strongly depend on the details of the flavor structure of new physics: even within the same model, LFV constraints can be much stronger or much weaker than LHC constraints LHC searches still leave a lot of place for LFV PMNS MEG CKM Calibbi, Hodgkinson, JonesPerez, Masiero, Vives '11 3

4 Experimental Signature of µ > e γ µ + e + Positron and photon are monochromatic (52.8 MeV), backtoback and produced at the same time; γ Accidental Background Radiative Muon Decay (RMD) DOMINANT e e µ µ µ ν ν ν γ γ ν 4

The MEG experiment A search for µ > e γ with the most intense DC muon beam in the world (3 x 10 7 µ/s @ PSI, Switzerland) 20092011 analysis (3.5 x 10 14 µ on target): BR(µ > e γ) < 5.

5 The MEG experiment A search for µ > e γ with the most intense DC muon beam in the world (3 x 10 7 PSI, Switzerland) analysis (3.5 x µ on target): BR(µ > e γ) < 5.7 x data presented here (7.5 x µ on target) LXe calorimeter for photon detection 16 drift chambers for positron tracking 30 scintillating bars for positron timing and trigger (Timing Counter, TC) 5

6 Trigger and DAQ FPGA based trigger system + (since 2011) multiple buffer: Beam intensity x acceptance Hz XEC Energy E > 45 MeV Hz eγ Timing Teγ < 10 ns.10 2 Hz eγ Angle 10 Hz Full digitization of all readout channels for offline analysis: custom digitization chip (DRS4) 6

7 Analysis Ingredients Relative Angle ACCURATE CALIBRATION of RECONSTRUCTION BIAS and e + Positron Energy ACCURATE CALIBRATION of ENERGY SCALE and Photon Energy ACCURATE CALIBRATION of ENERGY SCALE and LXe γ µ + DC Relative Time ACCURATE CALIBRATION of GLOBAL OFFSET and TC 7

8 Analysis Ingredients Relative Angle ACCURATE CALIBRATION of RECONSTRUCTION BIAS e Positron Energy ACCURATE CALIBRATION of ENERGY SCALE Photon Energy ACCURATE CALIBRATION of ENERGY SCALE and LXe γ µ + DC Relative Time ACCURATE CALIBRATION of GLOBAL OFFSET TC 8

efficiencies using LEDs and alpha sources weekly monitor of the

9 Photon Energy Reconstruction & Calibration (I) 800l LXe detector read out by 846 PMTs weekly calibration of PMT gains and quantum efficiencies using LEDs and alpha sources weekly monitor of the energy scale using a dedicated CW accelerator to produce photon via p + Li reactions 9

10 Photon Energy Reconstruction & Calibration (II) 800l LXe detector read out by 846 PMTs Resolution ~ 1.9% + Accurate calibration of the Energy Scale LH2 target BGO ~ monochromatic 55 MeV from π + p π 0 + n π 0 γ γ 10

11 Analysis Ingredients Relative Angle ACCURATE CALIBRATION of RECONSTRUCTION BIAS e + Positron Energy ACCURATE CALIBRATION of ENERGY SCALE and Photon Energy ACCURATE CALIBRATION of LXe γ µ + DC Relative Time ACCURATE CALIBRATION of GLOBAL OFFSET TC 11

over the whole spectrometer) Resolution ~ 300 kev + Accurate

12 Positron Energy Reconstruction & Calibrations 16 Drift Chamber modules Gradient Magnetic Field σr ~ 300 µm, σz ~ 1 mm Very light (~ 10 3 X0 over the whole spectrometer) Resolution ~ 300 kev + Accurate calibration of the Energy Scale Michel Muon Decay (µ > e ν ν) Energy Spectrum 12

13 Analysis Ingredients Relative Angle ACCURATE CALIBRATION of RECONSTRUCTION BIAS e + Positron Energy ACCURATE CALIBRATION of ENERGY SCALE Photon Energy ACCURATE CALIBRATION of LXe γ µ + DC Relative Time ACCURATE CALIBRATION of GLOBAL OFFSET and TC 13

Combined eγ observables Relative Time LXe calorimeter: photon time with ~ 60 ps resolution Timing counter: positron time with ~ 60 ps resolution DC spectrometer: time of

14 Combined eγ observables Relative Time LXe calorimeter: photon time with ~ 60 ps resolution Timing counter: positron time with ~ 60 ps resolution DC spectrometer: time of flight from the target to the TC with ~ 100 ps resolution Resolution ~ 130 ps + Accurate calibration of the time offset Time coincidences from Radiative Muon Decays (µ > e ν ν γ) 14

15 Analysis Ingredients Relative Angle ACCURATE CALIBRATION of RECONSTRUCTION BIAS and e + Positron Energy ACCURATE CALIBRATION of ENERGY SCALE Photon Energy ACCURATE CALIBRATION of LXe γ µ + DC Relative Time ACCURATE CALIBRATION of GLOBAL OFFSET TC 15

16 Combined eγ observables Relative Angle We have only one track in our signature: cannot make a real vertex γ TARGET e + decay point from the intersection of the DC track with the target plane LXe calorimeter: photon conversion point with ~ 5 mm resolution Relative angle from the combination of track direction + decay point + photon conversion point No physical process to accurately calibrate the relative angle: we have to rely on careful geometrical alignment procedures and separate measurements of LXe and DC resolutions 16

Highlights from the 20112013 Analysis Target position optically surveyed once per year and cross checked with reconstructed tracks (reconstructed position of holes in target): APLANARITY (3D scan) We

17 Highlights from the Analysis Target position optically surveyed once per year and cross checked with reconstructed tracks (reconstructed position of holes in target): APLANARITY (3D scan) We found a significative aplanarity of the target in data, then confirmed by a 3D scanner Intense activity needed to correct it and properly treat the systematic uncertainty We developed a method to increase the tracking efficiency by recovering events (~ 4%) where one turn of the positron inside the spectrometer was not reconstructed e+ annihilation in the DC γ e + We developed a method to reject events where a positron annihilate in the DC and produces a background photon in the calorimeter 17

Likelihood Analysis Likelihood analysis of 5 discriminating variables (Ee,Eγ, θeγ,φeγ,teγ): yearbyyear and eventbyevent PDFs careful treatment of correlations (from well understood geometrical

18 Likelihood Analysis Likelihood analysis of 5 discriminating variables (Ee,Eγ, θeγ,φeγ,teγ): yearbyyear and eventbyevent PDFs careful treatment of correlations (from well understood geometrical effects) Accidental Background PDFs are fully defined from data sidebands: very solid determination of the (largely) dominant background Signal and radiative decay PDFs by combining the results of the calibration procedures Normalization from the observed number of µ > e ν ν and RMD 18

19 Results (I) NACC = 7684 ± 103 NRMD = 663 ± 59 Magnified signal (BR = 4 x ) BR < 4.2 x 10 90% C.L. arxiv:

20 Results (II) Toy MC sensitivity Median UL = 5.3 x DATA 20

21 Physics Impact }E821 experiment MEGA (2002) One of many possible examples MSSM with large tanβ (Isidori, Mescia, Paradisi '07) Δaµ = aµ aµ SM 21

22 Physics Impact }E821 experiment MEGA (2002) One of many possible examples MEG MSSM with large tanβ (Isidori, Mescia, Paradisi '07) 22

23 The MEGII Experiment Larger LXe volume with finer light detector granularity Higher beam intensity Uniquevolume Drift Chamber RMD Veto Scintillator Tile TC 23

Better Resolution, Better pileup rejection Detector

24 MEGII Highlights (I) We developed UV sensitive MPPC to cover the inner face of the LXe calorimeter Better Resolution, Better pileup rejection Detector under commissioning σe ~ 1%, σposition ~ 2/5 mm (x,y/z) 24

25 MEGII Highlights (II) Scintillator tiles read out by SiPM 1/4 of the new TC assembled and took data at PSI last December (first Michel tracks observed) Complete detector under construction/ commissioning σt ~ 35 ps 25

26 MEGII Highlights (III) Drift Chamber wiring just started Expected to be completed by the end of the year σe ~ 130 kev, σangles ~ 5 mrad, 2x larger positron efficiency 26

27 MEGII Highlights (IV) RMD Veto 50% of background photons come from RMD w/ positron along the beam line Can be vetoed by detecting the positron in coincidence with the photon A new detector (LYSO + plastic scint.) already built > 16% better sensitivity Trigger and DAQ will be integrate in a single, compact system (WaveDream TDAQ) Also provides power and amplification for SiPM/MPPC 27

28 Expected Sensitivity MEGII is expected to start taking data with the full detector next year x10 improvement in sensitivity w.r.t. MEG 4 x in 4 years 28

29 Don t stop searching! 29

30 Backup 30

31 Target hole reconstruction Δx = 0.2 ± 0.1 mm 31

32 Likelihood plots 32

33 Normalization 33

The MEG/MEGII and Mu3e experiments at PSI. Angela Papa Paul Scherrer Institut on behalf of the MEG/MEGII and Mu3e collaborations

The MEG/MEGII and Mu3e experiments at PSI Angela Papa Paul Scherrer Institut on behalf of the MEG/MEGII and Mu3e collaborations Contents Introduction The world s most intense DC muon beam The MEG/MEGII