Mu2e Experiment at Fermilab
Steve Boi, Yuri Oksuzian Newcomers lunch
Steve Boi CRV at Mu2e experiment 1 Mu2e
Fermilab is actively pursuing the searches with high intensity beams: NOvA, Short- baseline neutrino, DUNE, Muon g-2, Mu2e… Mu2e will search for neutrino-less, coherent muon conversion into an electron
µ + N e + N ! Neutrino-less �→e- conversion is Charged Lepton Flavor Violation (CLFV) µ e , µ 3e, ⌧ e , ⌧ µ ... ! ! ! ! Mu2e can discover Charged leptonIn the flavor SM, �→ violatione- occurs at the rate of <10-50 – Signal observation at Mu2e is unambiguous sign of new physics 4 • Neutral lepton flavor violation– Indirectly probing high mass scales (>10 TeV) SUSY RPV SUSY has been observed ⌫e -50 ⌫µ -15 Second Higgs doublet RateSM < 10 RateBSM ~ 10 µ ⌫µ ⌫ µ ˜ µ u˜ e e e 0 e 0 0 µ e e µ˜ e˜ d • Induces CLFV H t W q q q q q q q q
• Induced rate: about 40 orders of magnitude below Steve Boi CRV at Mu2e experimentLeptoquarks 2 Z 0/anomalous couplings experimental limits Extra dimensions, etc. µ q µ e • CLFV observation would still be an unambiguous proof of New Physics Some reviews: LQ Z0 Kuno, Okada, 2001
Andrei Gaponenko 10 IF Seminar 2013-12-12 M. Raidal et al., 2008 q e q q
Andrei Gaponenko 17 IF Seminar 2013-12-12 What do we measure?
Mu2e will measure the ratio of �→e- conversions to the number of muon captures by Al nuclei:
(µ +(A,Z) e +(A,Z)) Rµe = (µ +(A,Z) ! ⌫ +(A,Z 1) ! µ
Steve Boi CRV at Mu2e experiment 3 Numerator
Mu2e will measure the ratio of �→e- conversions to the number of muon captures by Al nuclei:
(µ +(A,Z) e +(A,Z)) Rµe = (µ +(A,Z) ! ⌫ +(A,Z 1) ! µ
µ µ µ Al Al e
Ee- = 104.96 MeV
Steve Boi CRV at Mu2e experiment 4 Denominator
Mu2e will measure the ratio of �→e- conversions to the number of muon captures by Al nuclei:
(µ +(A,Z) e +(A,Z)) Rµe = (µ +(A,Z) ! ⌫ +(A,Z 1) ! µ
µ µ µ Al Mg* ⌫µ
n p BR = 61%
Steve Boi CRV at Mu2e experiment 5 Dominant background: Decay in orbit
Mu2e will measure the ratio of �→e- conversions to the number of muon captures by Al nuclei:
(µ +(A,Z) e +(A,Z)) Rµe = (µ +(A,Z) ! ⌫ +(A,Z 1) ! µ
⌫¯e µ µ µ Al Al ⌫µ
e
BR = 39%
Steve Boi CRV at Mu2e experiment 6 Mu2e Sensi vity
Mu2e will measure the ratio of �→e- conversions to the number of muon captures by Al nuclei:
(µ +(A,Z) e +(A,Z)) Rµe = (µ +(A,Z) ! ⌫ +(A,Z 1) ! µ
Mu2e single event sensitivity: R�e = 2.5×10-17
– Expect 40 events at R�e = 10-15
Mu2e planned sensitivity: R�e = 7×10-17 at 90% CL Mu2e needs to stop ~1018 muons – 3.6×1020 protons on target (POT) over 3 years Need to keep background small and well understood – Total expected background 0.4 events
Steve Boi CRV at Mu2e experiment 7 Mu2e apparatus
Production Transport Solenoid Detector Solenoid Solenoid
2.5 T 1.0 T 4.6 T 2.0 T
25 meters
Steve Boi CRV at Mu2e experiment 8 Mu2e apparatus
Production Transport Solenoid Detector Solenoid Solenoid
2.5 T 1.0 T 4.6 T Protons 2.0 T
Production Target
Protons strike production target to produce π- – Graded B-field reflects pions toward the transport solenoid
Steve Boi CRV at Mu2e experiment 9 Mu2e apparatus
Production Transport Solenoid Detector Solenoid Solenoid
2.5 T 1.0 T 4.6 T 2.0 T
Middle collimator
Curved trasport solenoid centers particles back Trasport solenoid: – Transports π-/µ- – Selects particle’s momentum and charge – Avoids direct line of sight
Collimator passes mostly negatives through Curved trasport solenoid Production separates charged particles Solenoid Steve Boi CRV at Mu2e experiment 10 Mu2e apparatus
Production Transport Solenoid Detector Solenoid Solenoid
2.5 T 1.0 T 4.6 T 2.0 T
Calorimeter Stopping Tracker Target
Muons stop on Al stopping target – 50% of µ- stop on the target – 1,000 POT → 2 stopped muons – Graded magnetic field reflects conversion electrons toward the tracker Conversion electron momentum and energy are measured in the tracker and calorimeter
Steve Boi CRV at Mu2e experiment 11
Mu2e Mu2e
opnn sga f 1 KVc ad sgiiat al im o 16 e/. h ne The KeV/c. 176 of sigma tail significant a and KeV/c, 115 of sigma component
most important for distinguishing conversion electrons from backgrounds, has a core core a has backgrounds, from electrons conversion distinguishing for important most
be well represented by the sum of two Gaussians two of sum the by represented well be
region. Current simulations indicate that the high side resolution of the Mu2e tracker Mu2e the of resolution side high the that indicate simulations Current region.
wy rm h sga rgo wie high a while region signal the from away
keV keV
critica
representing most of the rate from muon decays muon from rate the of most representing
the center is the stopping target. target. stopping the is center the
conversion electron (top) and a 53 MeV Michel electron (lower right) superimposed. The disk in in disk The superimposed. right) (lower electron Michel MeV 53 a and (top) electron conversion
Figure
Figure Figure
pass unobstructed through the hole in the center of the tracker. tracker. the of center the in hole the through unobstructed pass
in the tracker. tracker. the in
about 53 MeV, representing a very small fraction of the rate ( rate the of fraction small very a representing MeV, 53 about
orbit are below 60 MeV in energy ( energy in MeV 60 below are orbit
electrons from muo from electrons
temperature in vacuum. in temperature
system will be required for the electronics to maintain an appropriate operating operating appropriate an maintain to electronics the for required be will system
Chapter 4: Overview of the Mu2e Design Mu2e the of Overview 4: Chapter
rce rslto i an is resolution Tracker
h takr s eind o necp ol a ml fato o te si the of fraction small a only intercept to designed is tracker The
[7]
l background l
Conceptual Design Report Design Conceptual
4
4
. The requirement on the low side tail is less stringent since it smears background background smears it since stringent less is tail side low the on requirement The .
.
. 12
Tracker 12
. Cross sectional view of the Mu2e tracker with the trajectories of a 105 MeV MeV 105 a of trajectories the with tracker Mu2e the of view sectional Cross .
.
Lower energy electrons will curl in the field of the Detector Solenoid and and Solenoid Detector the of field the in curl will electrons energy Lower
s. s.
n decays n
The tracker The
-
important component in determining the level of
in
-
orbit. orbit.
lcrn wt eege salr hn 3 e (oe left), (lower MeV 53 than smaller energies with Electrons
is required to have a high
Figure 3.4 Figure
The vast majority of electrons from muon decay in in decay muon from electrons of majority vast The
-
-
in
side tail smears background into the signal signal the into background smears tail side
-
). Only electrons with energies greater than than greater energies with electrons Only ).
orbit, the miss tracker entirely. . The high The .
Knoepfel - FPCP 2014 41
-
side resolution, which is the the is which resolution, side
-
about 3%) about side resolution of of resolution side
The tracker in illustrated is This
gnificant flux of of flux gnificant
will be observed observed be will
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can
4
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15
t t
Low mass straw drift tubes 5 mm diameter straws – 15 �m Mylar walls
– Filled with 80/20 Ar/CO2 3.3 m 25 �m gold-plated tungsten sense wires 3.3 m 100 Straws = Panel; 6 Panel• End= Plane; product 2 Planeshas multiple = Station; modules Tracker with total = 18 of 23KStation straws • Module rotations optimized to ensure maximum coverage Steve Boi CRV at Mu2e experiment 12 Calorimeter
Two disks of BaF2 scin lla ng crystals
– BaF2 fast (<1 ns) me component and good energy resolu on (5%) Provides precise ming, PID, seed for tracking and triggering Complementary energy measurement
Tracker Calorimeter
Steve Boi CRV at Mu2e experiment 13 Cosmic Ray Veto
Mu2e expects 1 signal-like event per day induced by cosmic rays Cosmic Ray Veto(CRV) consists of 4-layer scin lla ng We require hits in at least 3 out of 4 layers for a valid cosmic ray muon background track
Details: • Area: 323 m2 • 82 modules 7 sizes • 5,152 counters • 10,254 fibers • 18,944 SiPMs
Steve Boi CRV at Mu2e experiment 14 CRV counter
Extruded plas c scin llator counters: 50 x 20 x 900-6600 mm3 Two 1.4-mm diameter wavelength shi ing fibers Readout: 2x2 mm2 SiPMs on each fiber end Two fibers per extrusion, up to four SiPMs for readout Glue two extrusions together to form di-counters
Steve Boi CRV at Mu2e experiment 15 CRV Modules
4 layers of counters with 3 layers of Al absorbers sandwiched between them: 16 counters/layer Layers are offset to avoid projec ve gaps between counters Total: 82 modules; two widths, five different lengths
Steve Boi CRV at Mu2e experiment 16 Cosmic Ray Background
The majority of cosmic ray muons are produced from galac c cosmic proton interac ons in Earth’s atmosphere
Cosmic ray muon rate at the surface is 100 Hz/m2 10 24. Cosmic rays 2 The rate is at maximum for ver cal muons, and decreases with the angle as cosin the atmosphere, the map of the overburdenθ at each detector,andthepropertiesofthe local medium in connecting measurements at various slant depths and zenith angles to the vertical intensity. Use of data from a range of angles allows a fixed detector to cover In order to shield against cosmic muons we need to build the detector several km under the ground a wide range of depths. The flat portion of the curve is due to muons produced locally by charged-current interactions of νµ.Theinsetshowstheverticalintensitycurveforwater …or cover Mu2e experiment with ac ve shielding - CRV and ice published in Refs. [59–62]. It is not as steep as the oneforrockbecauseofthe 24. Cosmiclower muonrays energy5 loss in water.
Altitude (km) 15 10 5 3 2 1 0 10000
1000
] _ –1 νµ + νµ sr 100 µ+ + µ− –1 s
–2
[m 10 11025 p + n
1 e+ + e− Vertical flux π+ + π− 0.1
0.01 110100 0 200 400 600 800 1000 Atmospheric depth [g cm–2] 5 −2 Figure 24.3: Vertical fluxes of cosmic rays in the atmosphere with E>Figure1GeV 24.6: Vertical muon intensity vs depth (1 km.w.e.= 10 gcm of standard estimated from the nucleonSteve flux of Eq.Boi (24.2). The points showCRV measurements atrock). Mu2e of Theexperiment experimental data are from: ♦:thecompilationsofCrouch[58],17 ": negative muons with Eµ > 1GeV[32–36]. Baksan [63], ◦:LVD[64], •:MACRO[65], #:Frejus[66],and△:SNO[67]. The shaded area at large depths represents neutrino-inducedmuonsofenergyabove the intensity curve for the parent pions serves to calibrate the atmospheric ν2GeV.Theupperlineisforhorizontalneutrino-inducedmuoµ beam [37]. ns, the lower one Because muons typically lose almost 2 GeV in passing through the atmosphere,for vertically the upward muons. Darker shading shows the muon fluxmeasuredby comparison near the production altitude is important for thesub-GeVrangeofthe SuperKamiokandeνµ(νµ) experiment. The inset shows the vertical intensity curve for energies. water and ice published in Refs. [59–62]. The flux of cosmic rays through the atmosphere is described by a set of coupled cascade equations with boundary conditions at the top of the atmosphere to match the primary spectrum. Numerical or Monte Carlo calculations are needed to account accurately for decay and energy-loss processes, and for the energy-dependences of the cross sections and of the primary spectral index γ.Approximateanalyticsolutionsare,however,usefulin
February 16, 2012 14:07
February 16, 2012 14:07 Cosmic Ray Background
Cosmic rays can interact with detector components producing 105 MeV electron, faking a conversion signal To be er understand CRV design, simula ons are underway Currently we simulated 28 billion cosmic ray muons, only 2% of total number expected over experiment life me To achieve experiment’s designed sensi vity, detec on inefficiency is required to be no worse than 10-4
Steve Boi CRV at Mu2e experiment 18 Few challenges: radia on noise
Neutron and gamma fluxes from beam interactions cause problems to CRV operations ‣ Produce hits at the CRV, faking cosmic ray muons and hence increasing total Mu2e dead-time
Accidental Semi-correlated Fully-correlated
Total dead-time needs to be small (5-10%)
Steve Boi CRV at Mu2e experiment 19 Summary
Mu2e has a great discovery poten al and can reveal New Physics Mu2e will improve over previous conversion experiments by 4 orders of magnitude and will probe new physics mass scales of 104 TeV Mu2e will provide complimentary informa on to the LHC and test the existence of new par cles that are too heavy to be produced directly at colliders Experimental design is mature. Construc on has started Cosmic ray veto is an essen al component for the Mu2e experiment by suppressing the backgrounds by 4 orders of magnitude Poten al discovery in the next decade Poten al discovery within the next decade…
Steve Boi CRV at Mu2e experiment 20