002824583 001__ 2824583
002824583 005__ 20231213053243.0
002824583 0248_ $$aoai:cds.cern.ch:2824583$$pcerncds:FULLTEXT$$pcerncds:CERN:FULLTEXT$$pcerncds:CERN
002824583 037__ $$9arXiv$$aarXiv:2203.01981$$chep-ex
002824583 035__ $$9arXiv$$aoai:arXiv.org:2203.01981
002824583 035__ $$9Inspire$$aoai:inspirehep.net:2046439$$d2023-12-12T16:08:28Z$$h2023-12-13T03:00:33Z$$mmarcxml$$ttrue$$uhttps://inspirehep.net/api/oai2d
002824583 035__ $$9Inspire$$a2046439
002824583 041__ $$aeng
002824583 100__ $$aAltmannshofer, W.$$uUC, Santa Cruz$$vUniversity of California Santa Cruz
002824583 245__ $$9arXiv$$aPIONEER: Studies of Rare Pion Decays
002824583 269__ $$c2022-03-03
002824583 300__ $$a68 p
002824583 520__ $$9arXiv$$aA next-generation rare pion decay experiment, PIONEER, is strongly motivated by several inconsistencies between Standard Model (SM) predictions and data pointing towards the potential violation of lepton flavor universality. It will probe non-SM explanations of these anomalies through sensitivity to quantum effects of new particles even if their masses are at very high scales. Measurement of the charged-pion branching ratio to electrons vs. muons $R_{e/\mu}$ is extremely sensitive to new physics effects. At present, the SM prediction for $R_{e/\mu}$ is known to 1 part in $10^4$, which is 15 times more precise than the current experimental result. An experiment reaching the theoretical accuracy will test lepton flavor universality at an unprecedented level, probing mass scales up to the PeV range. Measurement of pion beta decay, $\pi^+\to \pi^0 e^+ \nu (\gamma)$, with 3 to 10-fold improvement in sensitivity, will determine $V_{ud}$ in a theoretically pristine manner and test CKM unitarity, which is very important in light of the recently emerged tensions. In addition, various exotic rare decays involving sterile neutrinos and axions will be searched for with unprecedented sensitivity. The experiment design benefits from experience with the recent PIENU and PEN experiments at TRIUMF and the Paul Scherrer Institut (PSI). Excellent energy and time resolutions, greatly increased calorimeter depth, high-speed detector and electronics response, large solid angle coverage, and complete event reconstruction are all critical aspects of the approach. The PIONEER experiment design includes a 3$\pi$ sr 25 radiation length calorimeter, a segmented low gain avalanche detector stopping target, a positron tracker, and other detectors. Using intense pion beams, and state-of-the-art instrumentation and computational resources, the experiments can be performed at the PSI ring cyclotron.
002824583 540__ $$3preprint$$aCC BY 4.0$$uhttp://creativecommons.org/licenses/by/4.0/
002824583 595_D $$aG$$d2022-03-09$$sfullabs
002824583 595_D $$aG$$d2022-03-21$$sprinted
002824583 65017 $$2arXiv$$aphysics.ins-det
002824583 65017 $$2SzGeCERN$$aDetectors and Experimental Techniques
002824583 65017 $$2arXiv$$ahep-ph
002824583 65017 $$2SzGeCERN$$aParticle Physics - Phenomenology
002824583 65017 $$2arXiv$$ahep-ex
002824583 65017 $$2SzGeCERN$$aParticle Physics - Experiment
002824583 690C_ $$aCERN
002824583 690C_ $$aPREPRINT
002824583 693__ $$aPIONEER
002824583 700__ $$aGori, S.$$uUC, Santa Cruz$$vUniversity of California Santa Cruz
002824583 700__ $$aGodoy, M.$$uUC, Santa Cruz$$vUniversity of California Santa Cruz
002824583 700__ $$aGrillo, A.$$uUC, Santa Cruz$$vUniversity of California Santa Cruz
002824583 700__ $$aMazza, S.$$uUC, Santa Cruz$$vUniversity of California Santa Cruz
002824583 700__ $$aOtt, J.$$uUC, Santa Cruz$$vUniversity of California Santa Cruz
002824583 700__ $$aSchumm, B.$$uUC, Santa Cruz$$vUniversity of California Santa Cruz
002824583 700__ $$aSeiden, A.$$uUC, Santa Cruz$$vUniversity of California Santa Cruz
002824583 700__ $$aTarka, M.$$uUC, Santa Cruz$$vUniversity of California Santa Cruz
002824583 700__ $$aBinney, H.$$uWashington U., Seattle$$vUniversity of Washington
002824583 700__ $$aGarcia, A.$$uWashington U., Seattle$$vUniversity of Washington
002824583 700__ $$aHertzog, D.$$uWashington U., Seattle$$vUniversity of Washington
002824583 700__ $$aHodge, Z.$$uWashington U., Seattle$$vUniversity of Washington
002824583 700__ $$aKammel, P.$$uWashington U., Seattle$$vUniversity of Washington
002824583 700__ $$aLaBounty, J.$$uWashington U., Seattle$$vUniversity of Washington
002824583 700__ $$aRoehnelt, R.$$uWashington U., Seattle$$vUniversity of Washington
002824583 700__ $$aBlucher, E.$$uChicago U.$$vUniversity of Chicago
002824583 700__ $$aBryman, D.$$uBritish Columbia U.$$uTRIUMF$$vUniversity of British Columbia and TRIUMF
002824583 700__ $$aChen, S.$$uTsinghua U., Beijing, Dept. Eng. Phys.$$vTsinghua University
002824583 700__ $$aCirigliano, V.$$uLos Alamos$$vLos Alamos National Laboratory
002824583 700__ $$aCorrodi, S.$$uArgonne$$vArgonne National Laboratory
002824583 700__ $$aHernandez, C. Ortega$$uMexico U., ICN$$vUniversidad Nacional Autonoma de Mexico
002824583 700__ $$aCuen-Rochin, S.$$uPorto U.$$uINESC-TEC, Porto$$vTec de Monterrey
002824583 700__ $$aCzarnecki, A.$$uAlberta U.$$vUniversity of Alberta
002824583 700__ $$aDiCanto, A.$$uBrookhaven$$vBrookhaven National Laborory
002824583 700__ $$aJaffe, D.$$uBrookhaven$$vBrookhaven National Laborory
002824583 700__ $$aKettel, S.$$uBrookhaven$$vBrookhaven National Laborory
002824583 700__ $$aTischenko, V.$$uBrookhaven$$vBrookhaven National Laborory
002824583 700__ $$aTricoli, A.$$uBrookhaven$$vBrookhaven National Laborory
002824583 700__ $$aWorcester, E.$$uBrookhaven$$vBrookhaven National Laborory
002824583 700__ $$aDoria, L.$$uU. Mainz, PRISMA$$vJohannes Gutenberg University Mainz
002824583 700__ $$aGorchtein, M.$$uU. Mainz, PRISMA$$vJohannes Gutenberg University Mainz
002824583 700__ $$aRies, D.$$uU. Mainz, PRISMA$$vJohannes Gutenberg University Mainz
002824583 700__ $$aGaponenko, A.$$uFermilab$$vFermilab
002824583 700__ $$aKiburg, B.$$uFermilab$$vFermilab
002824583 700__ $$aMott, J.$$uFermilab$$vFermilab
002824583 700__ $$aPolly, C.$$uFermilab$$vFermilab
002824583 700__ $$aGibbons, L.$$uCornell U.$$vCornell University
002824583 700__ $$aLabe, K.$$uCornell U.$$vCornell University
002824583 700__ $$aGlaser, C.$$uVirginia U.$$vUniversity of Virginia
002824583 700__ $$aPočanić, D.$$uVirginia U.$$vUniversity of Virginia
002824583 700__ $$aGorringe, T.$$uU. Kentucky, Lexington$$vUniversity of Kentucky
002824583 700__ $$aHoferichter, M.$$uBern U.$$vUniversity of Bern
002824583 700__ $$aIto, S.$$uKEK, Tsukuba$$vKEK
002824583 700__ $$aMihara, S.$$uKEK, Tsukuba$$vKEK
002824583 700__ $$aIwamoto, T.$$uCERN$$vUniversity of Tokyo
002824583 700__ $$aMori, T.$$uCERN$$vUniversity of Tokyo
002824583 700__ $$aOotani, W.$$uCERN$$vUniversity of Tokyo
002824583 700__ $$aWataru, T.$$uCERN$$vUniversity of Tokyo
002824583 700__ $$aLangenegger, U.$$uPSI, Villigen$$vPSI
002824583 700__ $$aSchwendimann, P.$$uPSI, Villigen$$vPSI
002824583 700__ $$aLangenegger, U.$$uWashington U., Seattle$$uPSI, Villigen$$vUniversity of Washington$$vPSI
002824583 700__ $$aMalbrunot, C.$$uCERN$$vCERN
002824583 700__ $$aMischke, R.$$uTRIUMF$$vTRIUMF
002824583 700__ $$aNumao, T.$$uTRIUMF$$vTRIUMF
002824583 700__ $$aPachal, K.$$uTRIUMF$$vTRIUMF
002824583 700__ $$aSher, A.$$uTRIUMF$$vTRIUMF
002824583 700__ $$aVelghe, B.$$uTRIUMF$$vTRIUMF
002824583 700__ $$aWong, V.$$uTRIUMF$$vTRIUMF
002824583 700__ $$aSoter, A.$$uETH, Zurich (main)$$vETH Zurich
002824583 700__ $$aShrock, R.$$uSUNY, Stony Brook$$vStony Brook University
002824583 700__ $$aSullivan, T.$$uVictoria U.$$vUniversity of Victoria
002824583 710__ $$gPIONEER Collaboration
002824583 8564_ $$uhttps://lss.fnal.gov/archive/2022/pub/fermilab-pub-22-613-ppd.pdf$$yFermilab Library Server
002824583 8564_ $$82383774$$s14019871$$uhttp://cds.cern.ch/record/2824583/files/2203.01981.pdf$$yFulltext
002824583 8564_ $$82383775$$s18173$$uhttp://cds.cern.ch/record/2824583/files/PmaxSim.png$$y00027 Left: AC-LGAD strip simulated waveform with TCAD Silvaco. The sensor is a 200\,$\mu$m pitch strip sensors with N+ sheet resistivity of 500\,$\Omega$. Right: Pulse maximum (normalized) as a function of position for a strip with 80\,$\mu$m width and 200\,$\mu$m pitch. Left edge of the plot is the center of the readout strip. Curves are for data (FNAL testbeam) and TCAD Silvaco simulation with several N+ sheet resistivity.
002824583 8564_ $$82383776$$s71598$$uhttp://cds.cern.ch/record/2824583/files/tail_fraction.png$$y00012 Left: The energy deposited by monoenergetic 69.3\,MeV $e^{+}$ from \pie~ decays in a 25\,$X_0$ calorimeter with an energy resolution of 1.5\% vs. the angle Theta with respect to the beam axis. The grey bands indicate the boundaries of the fiducial volume region (here, $30^{\circ}$). Right: The shower tail fraction below 58\,MeV vs. the calorimeter depth in radiation lengths for the 69.3\,MeV $\pi \rightarrow e \nu$ events.
002824583 8564_ $$82383777$$s38488$$uhttp://cds.cern.ch/record/2824583/files/FNAL_TB.png$$y00025 Left: prototype BNL AC-LGAD strip sensor with 80\,$\mu$m wide strips and pitch of (left to right) 100, 150, 200\,$\mu$m. Right: sensor response ($P_{max}$) as a function of position (perpendicular to the strip) of two strips with 200~$\mu m$ of pitch~\cite{ACLGADpico}. The dashed lines highlight the position of the two strips in the plot. Data taken at the FNAL 120\,GeV proton test beam facility.
002824583 8564_ $$82383778$$s300466$$uhttp://cds.cern.ch/record/2824583/files/LXECal.png$$y00014 Concept design of the liquid xenon calorimeter. For scale, the lid is 3.05 m diameter. The yellow circles are merely representative of the photosensors; they are not placed accurately.
002824583 8564_ $$82383779$$s111588$$uhttp://cds.cern.ch/record/2824583/files/LYSO-figs.png$$y00021 Possible use of an inner array of tapered LYSO crystals within the open volume of the existing PEN CsI calorimeter. a) Opened view showing in blue the array of LYSO crystals that matches one-to-one to the existing geometry of the PEN crystals shaded in gray. b) An example array ideal for testing the concept. c) An individual pentagonal crystal, 16$X_0$ in depth. Each such crystal would be read out by a thin array of SiPMs.
002824583 8564_ $$82383780$$s10156$$uhttp://cds.cern.ch/record/2824583/files/high_stats_tail_example_final.png$$y00001 The positron energy spectra from muon decays (blue) and from \pie~ decays (orange) for a calorimeter resolution of 1.5\% and a depth of $25\,X_0$. The simulation includes energy losses owing to photonuclear interactions.
002824583 8564_ $$82383781$$s83073$$uhttp://cds.cern.ch/record/2824583/files/ATAR_scheme_2.png$$y00011 Left: \atar\ position in the beam line. Right: Concept schematic design of the \atar. The flex from the first, third and fifth sensors is directed in and out of the page. The modules are attached on the HV side and with a few \si{\micro\metre} of separation on the strip side. 48 sensors are coupled in 24 pairs.
002824583 8564_ $$82383782$$s140467$$uhttp://cds.cern.ch/record/2824583/files/LGAD_energy_linearity.png$$y00022 Left: Peak of the pulse maximum distribution vs X-ray energy, data is for a HPK 50~$\mu$m LGAD at different gain levels. Right: Fractional energy resolution as a function of X-ray energy, data is for three HPK LGADs of 35~$\mu$m, 50~$\mu$m and 80~$\mu$m of thickness.
002824583 8564_ $$82383783$$s61990$$uhttp://cds.cern.ch/record/2824583/files/pions_YYp.png$$y00008 : Preliminary pion phase space distributions at the \calo\ center position for 65~MeV/$c$ pions with decay disabled from the \gbl\ simulation of $\pi$E5. Left: Horizontal. Right: Vertical. The calculated emitance $\epsilon$ for each is included in the plot as text. The non-Gaussian structure of these phase spaces present a challenge in correctly modeling the beam transport. : Caption not extracted
002824583 8564_ $$82383784$$s128918$$uhttp://cds.cern.ch/record/2824583/files/EventTypes_vector.png$$y00002 Illustration of event types in the $\pi \rightarrow e$ and $\pi \rightarrow \mu \rightarrow e$ chains. The stars are indicative of the energy deposited at the Bragg peak for pions (red) or muons (purple) that stop in the segmented ATAR. The main channels of interest include 1) the $\pi \rightarrow e$ ``signal channel'' decay that emits a monoenergetic 69.3\,MeV positron; 2) the dominant $\pi \rightarrow \mu$ decay, where the 4.1\,MeV muon travels up to 0.8\,mm and also stops in the ATAR before emitting a positron. Events 3) and 4) represent situations that can confuse the classification of events into categories 1) or 2). In 3) the pion decays within the ATAR prior to stopping; the muon stop can then appear as a pion stop. In 4), the pion stops, and the decay muon (very rarely, but importantly) decays in the short time prior to stopping. Because it is a decay in flight, the Lorentz boost can push the positron energy beyond the 52.3\,MeV endpoint. The ATAR is being designed to distinguish these event patterns.
002824583 8564_ $$82383785$$s61942$$uhttp://cds.cern.ch/record/2824583/files/pioneer_drawing_largerfonts.png$$y00000 Layout of the PIONEER rare pion decay experiment. The intense positive pion beam enters from the left and is brought to rest in a highly segmented active target (ATAR). Decay positron trajectories are measured from the ATAR to an outer electromagnetic calorimeter (CALO) through a tracker. The CALO records the positron energy, time and location.
002824583 8564_ $$82383786$$s4910956$$uhttp://cds.cern.ch/record/2824583/files/sensor.png$$y00024 Left: prototype BNL AC-LGAD strip sensor with 80\,$\mu$m wide strips and pitch of (left to right) 100, 150, 200\,$\mu$m. Right: sensor response ($P_{max}$) as a function of position (perpendicular to the strip) of two strips with 200~$\mu m$ of pitch~\cite{ACLGADpico}. The dashed lines highlight the position of the two strips in the plot. Data taken at the FNAL 120\,GeV proton test beam facility.
002824583 8564_ $$82383787$$s25140$$uhttp://cds.cern.ch/record/2824583/files/PEN_apparatus_gen.png$$y00020 :
002824583 8564_ $$82383788$$s61307$$uhttp://cds.cern.ch/record/2824583/files/r-t.png$$y00004 Range-energy (left) and momentum-energy (right) relations for pions and muons. Muons from \pdar\ have 4.12 MeV kinetic energy and travel 0.8 mm in Si.
002824583 8564_ $$82383789$$s58997$$uhttp://cds.cern.ch/record/2824583/files/resolution_scan_25_x0_michel.png$$y00013 The effect of energy resolution on a 25\,$X_0$ calorimeter. The events indicated with a solid line are monoenergetic 69.3\,MeV $e^+$ from $\pi \rightarrow e \nu$ decay. The events indicated with a dashed line are the Michel spectrum from muon decay. The dashed grey line at 53 MeV represents the nominal endpoint of the Michel spectrum.
002824583 8564_ $$82383790$$s56707$$uhttp://cds.cern.ch/record/2824583/files/Analysis.png$$y00019 The upper panel shows the positron energy spectrum with the red line indicating $E_{cut}$. The lower panels show the time distributions for events below and above $E_{cut}$. The black histograms are data, the red curve is the $\pi^+ \to \mu^+ \to e^+$ signal, and the blue line is the $\pi^+ \to e^+ \nu$ signal. The other histograms in various colors are the background terms related to pile-up, muon DIF, and other effects discussed in Ref.~\cite{PiENu:2015seu}.
002824583 8564_ $$82383791$$s45034$$uhttp://cds.cern.ch/record/2824583/files/Simulation.png$$y00026 Left: AC-LGAD strip simulated waveform with TCAD Silvaco. The sensor is a 200\,$\mu$m pitch strip sensors with N+ sheet resistivity of 500\,$\Omega$. Right: Pulse maximum (normalized) as a function of position for a strip with 80\,$\mu$m width and 200\,$\mu$m pitch. Left edge of the plot is the center of the readout strip. Curves are for data (FNAL testbeam) and TCAD Silvaco simulation with several N+ sheet resistivity.
002824583 8564_ $$82383792$$s56659$$uhttp://cds.cern.ch/record/2824583/files/event_display1_vt.png$$y00009 Simulated example displays of pion decay events in the \atar. Pions enter horizontally from the left; the red dotted lines show the positions of the pion stops. The color of the bars indicates the deposited energy. Left column: X-Z (top) and Y-Z (bottom) strip views of a \pie\ event. Right column: Same views of a \pme\ event. The blue dotted line shows the position of the decay muon stop.
002824583 8564_ $$82383793$$s143446$$uhttp://cds.cern.ch/record/2824583/files/DAQschematic.png$$y00018 Schematic of the data acquisition system showing the frontend layer for data readout and experiment configuration, the backend layer for event assembly and data storage, and the analysis layer for data quality monitoring. The number of frontends and the topology of the FPGA-to-frontend and frontend-to-backend networks will be based on the calorimeter, ATAR and FPGA technology choices.
002824583 8564_ $$82383794$$s936933$$uhttp://cds.cern.ch/record/2824583/files/ATAR.png$$y00010 Left: \atar\ position in the beam line. Right: Concept schematic design of the \atar. The flex from the first, third and fifth sensors is directed in and out of the page. The modules are attached on the HV side and with a few \si{\micro\metre} of separation on the strip side. 48 sensors are coupled in 24 pairs.
002824583 8564_ $$82383795$$s12713$$uhttp://cds.cern.ch/record/2824583/files/PiE5_Rates.png$$y00006 The rates for pions and muons at the entrance to the experimental area (QSB43) and reaching the center of the calorimeter, calculated in the $\pi$E5 \gbl\ simulation.
002824583 8564_ $$82383796$$s31858$$uhttp://cds.cern.ch/record/2824583/files/TriggerBackend.png$$y00016 Proposed topology of the trigger and subdetector readout systems.
002824583 8564_ $$82383797$$s482447$$uhttp://cds.cern.ch/record/2824583/files/G4BLSIM_PiE5_Labeled.png$$y00005 The \gbl\ model of the $\pi$E5 beamline including a stand-in calorimeter.
002824583 8564_ $$82383798$$s859987$$uhttp://cds.cern.ch/record/2824583/files/target.png$$y00003 Beam counters and \atar. An active degrader disk (not shown) is optional, and only required for p$>$55 MeV/c. The beam detectors systems LGAD1 and LGAD2 provide an event by event trajectory for entering particles. It is conceivable that they can be rotated out of the beam for production running at the lowest operating momenta.
002824583 8564_ $$82383799$$s68004$$uhttp://cds.cern.ch/record/2824583/files/LGAD_energy_resolution.png$$y00023 Left: Peak of the pulse maximum distribution vs X-ray energy, data is for a HPK 50~$\mu$m LGAD at different gain levels. Right: Fractional energy resolution as a function of X-ray energy, data is for three HPK LGADs of 35~$\mu$m, 50~$\mu$m and 80~$\mu$m of thickness.
002824583 8564_ $$82383800$$s67848$$uhttp://cds.cern.ch/record/2824583/files/pions_XXp.png$$y00007 : width=0.4\textwidth,height=0.4\textwidth
002824583 8564_ $$82383801$$s163620$$uhttp://cds.cern.ch/record/2824583/files/times.png$$y00015 Positron rates after PI per second in 1\,ns time bins. \pie\ positron rates are multiplied by a factor 100. \pme\ rates generated by PI shown in red and positron rates from old muons, i.e. from accidental pions, shown in blue.
002824583 8564_ $$82383802$$s27414$$uhttp://cds.cern.ch/record/2824583/files/CaloDAQ.png$$y00017 Proposed calorimeter digitization and readout. The 12 channel digitizer boards utlize the dual channel AD9234 12 bit, 1 GSPS ADCs, Xilinx Ultrascale FPGAs for contro, and Samtec Firefly\textsuperscript{TM} high speed communications to a CMS APOLLO board. The APOLLO board can receive up to 22 boards in this configuration -- instrumenting quadrant of an order 1000 channel calorimeter.
002824583 8564_ $$82423076$$s13692321$$uhttp://cds.cern.ch/record/2824583/files/3534af773bf4ed75e6fb7f4e01c05529.pdf$$yFulltext
002824583 960__ $$a11
002824583 980__ $$aPREPRINT