Detectors for e + /e − Identification in FGT R. Petti University of South Carolina, USA DUNE ND Working Group Meeting December 3, 2015 Roberto Petti USC
THE DUNE FGT CONCEPT ✦ Evolution from the NOMAD experiment -.%/$%0(34*5 ✦ High resolution spectrometer < & ; : $ B = 0 . 4 T 9 ( & -.%/$%0()*+, ' . 8 7 6 ✦ Low density ”transparent” tracking , + ρ ∼ 0 . 1 g/cm 3 * X 0 ∼ 5 m ) ( ' & % !"" % $ 9 # ( ✦ Combined particle ID & tracking @ ? > A?B(9 #$12/$%0()*+, for precise reconstruction of 4-momenta ⇒ e − /e + ID, γ ● Transition Radiation = A?B(9 ⇒ Proton ID, π + / − , K + / − ● dE/dx = #$12/$%0(34*5 ✦ Tunable thin target(s) spread over entire =$:;&<( tracking volume = ⇒ target mass ∼ 7t 1.7'5 ✦ 4 π ECAL in dipole B field #$%%&'( ⇒ µ + /µ − ✦ 4 π µ -Detector (RPC) = 34*5 ”ELECTRONIC BUBBLE CHAMBER” WITH O (10 8 ) EVENTS Roberto Petti USC
DETECTION OF e − /e + IN FGT ✦ Key feature reconstruction of e − /e + as single CHARGED TRACKS, as opposed to compact electromagnetic showers: ● Require low density ( < 0 . 1 g/cm 3 ) tracking with thickness ∼ 1 X 0 and track sampling O (10 − 3 ) ; ● Require magnetic field to separate e + from e − and reconstruct γ converted in tracking volume ⇒ With B=0.4 T e − /e + tracks can be reconstructed down to ∼ 80 MeV = ● Provide accurate 4-momentum measurement of e − /e + (measure both ⃗ p and E) ✦ Continuous e − /e + identification fully integrated into tracking volume: ● Transition Radiation (TR) only produced by e − /e + with γ > 1000 ; ● Ionization dE/dx provides additional e/ π separation in the DUNE energy range; ⇒ Measurement of energy deposition in active straws sensitive to both = ✦ Matching of extrapolated e − /e + tracks with ECAL electromagnetic showers (clusters): ● Energy deposition in ECAL powerful e/ π rejection; ● Transverse and longitudinal profile of electromagnetic showers (clusters) in ECAL provides additional e/ π rejection; ● Reconstruction of Bremsstrahlung γ ’s emitted by e − /e + in the bending plane from ECAL and STT (conversions). Roberto Petti USC
THE STRAW TUBE TRACKER ✦ Main parameters of the STT design: !""#$%&'()#*%$&() ++#,,#-..)*'(/# ● Straw inner diameter 9 . 530 ± 0 . 005 mm; FE electronics 0)1)-2)$#%3#45**# 16278#()-963:#0%%*# ● Straw walls 70 ± 5 µm Kapton 160XC370/100HN IO boards ;%0#2863#2-0:)2<.= ( ρ = 1 . 42 , X 0 = 28 . 6 cm , each straw < 5 × 10 − 4 X 0 ); ● Wire W gold plated 20 µm diameter; ● Wire tension around 50g; ● Operate with 70%/30% Xe/CO 2 gas mixture. ● Straws are arranged in double layers of 336 straws glued together (epoxy glue) inserted in C-fiber composite frames; ● Double module assembly (XX+YY) with FE electronics (each XX+YY tracking module ∼ 2 × 10 − 3 X 0 ); Text ● Readout at both ends of straws (IO & FE boards on all sides of each XX+YY STT module); Straw layer Straw layer ● 160 modules arranged into 80 double modules over ∼ 6 . 4 m (total 107,520 straws). ⇒ Total tracking length ∼ 0 . 3 X 0 = ✦ Add dedicated (anti)neutrino thin target(s) to each >?** STT double module keeping the average STT den- ∼ 2 × 10 − 3 X 0 sity ∼ 0 . 1 g/cm 3 for required target mass. Roberto Petti USC
RADIATOR TARGETS $%%&'()*+,&#(')+, ✦ Design and physics performance (Transition Radia- FE electronics --&..&/00,#*+1& tion) of radiator targets optimized (docdb # 9766) 2345&6/'3/4(6&7(3+0 IO boards ⇒ Mechanical engineering model available = ✦ Radiator targets integrated at both sides of each STT (double layer) module to minimize overall thickness (foils could be removed if needed): ● Embossed polypropylene foils, 25 µm thick, 125 µm gaps; ● Total number of radiator foils 240 per XXYY module, arranged into 4 radiators composed of 60 foils each; ● Total radiator mass in each XXYY module: Straw layer Straw layer 69.1 kg, 1 . 25 × 10 − 2 X 0 . Radiator foils ⇒ The radiator represents 82.6% = 60 x 4 = 240 of the total mass of each STT module ⇒ Tunable for desired statistics & p resolution = !"## ∼ 1 . 4 × 10 − 2 X 0 Roberto Petti USC
Sketch of the embossing pattern for the polypropylene radiator foils Roberto Petti USC
FGT G4 simulation: 1 GeV e + 2.5 m 5.0 m 5.0 m 5.0 m ρ = 0 . 1 g/cm 3 , X 0 = 500 cm, track sampling 1.9cm/500cm = 0.38% track sampling ⊥ 0.95cm/500cm = 0.19% Roberto Petti USC
ND G4 simulation: 1 GeV e FD G4 simulation: 1 GeV e + 2.5 m 5.0 m ρ = 1 . 4 g/cm 3 , X 0 = 14 cm, track sampling 4.667mm/140mm = 3.33% Roberto Petti USC
� � � � � TR photons emitted within a cone 1 / γ < 1 mrad from the track direction � Absorption length (mm) � ��������������������������� Photon energy (keV) %7(,5$89:9;$$$$$$$$$$$$$$<"(,+-.7"$/#=>+#($$$?)@#$A Xe gas has an absorption length 10 times smaller than Ar and � straw diameter Use a proven gas mixture with 70% Xe and 30% CO 2 for TR detection Need closed gas system to minimize Xe leakage (Xe is expensive) and avoid Xe content in gas volume outside straws (flush with CO 2 ) � � � � � � � � �� � Roberto Petti USC � � �� � � � � �� � � � � � � � �
TRANSITION RADIATION ) 0.18 -1 l =15 µ m, l =300 µ m, N =100 TR yield (keV 1 0.16 2 f γ =3914 0.14 ✦ Simulation of Transition Radiation (TR) based on γ =1957 0.12 formalism by Garibian (1972), Cherry (1975) = 978 γ 0.1 γ = 391 = ⇒ Narrow energy range ∼ few keV 0.08 0.06 0.04 ✦ Radiator design optimized for TR performance: 0.02 5 10 15 20 25 30 ● TR build-up over many interfaces; 0.16 l =300 µ m, N =100, γ =3914 2 f ● Self-absorption of lower part of energy spectrum; 0.14 l =40 m µ 1 ● Need compact radiarors to keep large tracking sampling. 0.12 l =20 m µ 1 l =10 m µ 0.1 1 = ⇒ Select 25 µm foils, 125 µm spacing l = 5 µ m 1 0.08 0.06 0.04 ✦ On average ∼ 1 TR photon with E > 5 keV 0.02 detected in a single STT module from a 1 GeV e 0.2 l = 15 m, N =100, =3914 µ γ 1 f 0.18 l =900 µ m ✦ dE/dx in straws are of the same order as TR at 0.16 2 l =300 m µ 0.14 2 energies of few GeV: a 5 GeV e( π ) has a probability l =100 m µ 0.12 2 l = 30 µ m 0.1 ∼ 41%(18%) of depositing E > 6 keV 2 0.08 0.06 0.04 0.02 5 10 15 20 25 30 Energy (keV) Roberto Petti USC
Ioniza'on dE/dx, E=5 GeV Roberto Petti USC
COMPARISON WITH NOMAD ✦ Continuous TR+dE/dx detection over entire STT volume, NOMAD only limited forward coverage ⇒ Improved acceptance and e + /e − ID = ✦ NOMAD TRD configuration: ● 9 radiators made of 315 (C 3 H 6 ) n foils each; ● foils 15 µm thick, with 250 µm air gaps; ● 16 mm diameter straws without tracking capability. ⇒ Total 2,835 foils over ∼ 154 cm length = ✦ Need ∼ 12 double STT modules (4 straw layers each) to match the total foils of the NOMAD TRD ⇒ More compact design with length ∼ 92 cm = ✦ Opposite e ff ects in STT: ● Smaller air gaps and thicker foils reduce TR production with respect to NOMAD; ● Larger Xe volume more uniformly distributed within radi- ator foils increases TR detection e ffi ciency. Roberto Petti USC
THE ELECTROMAGNETIC CALORIMETER ✦ Glo-Sci-51,23 measure absolute and relative ν µ , ν e and ¯ ν µ , ¯ ν e spectra separately. Glo-Sci-24 measure rates, kinematic distributions and topologies of bkgnd processes ⇒ reconstruction of e + /e − , γ with accuracy comparable to µ + /µ − and FD = = ⇒ containment of > 90% of shower energy NDC-L2-29,37 √ = ⇒ energy resolution < 6% / E NDC-L2-38 ✦ Based upon the design of the T2K ND-280 ECAL (to be further optimized) ✦ Sampling electromagnetic calorimeter with Pb absorbers and alternating horizontal and vertical (XYXYXY....) 3 . 2 m × 2 . 5 cm × 1 cm scintillator bars readout at both ends by ∼ 1 mm diameter extruded WLS fibers and SiPM ● Forward ECAL: 60 layers with 1.75 mm Pb plates = ⇒ 20 X 0 ● Barrel ECAL: 18 layers with 3.5 mm Pb plates = ⇒ 10 X 0 ● Backward ECAL: 18 layers with 3.5 mm Pb plates = ⇒ 10 X 0 Roberto Petti USC
WLS&fiber Pb&plate X&Sci.&bars 3.28m Pb&plate WLS&fiber Y&Sci.&bars Pb&plate X&Sci.&bars 3 Pb&plate 81cm . 2 8 m WLS&fiber Y&Sci.&bars Pb&plate X&Sci.&bars Pb&plate WLS&fiber Y&Sci.&bars Pb&plate Front&End&Board& (64&Channel)& Barrel&ECAL&module Barrel&ECAL ! Forward&ECAL& mass&21.7&tons 3.28m 27.5cm 1.65m ! Barrel&ECAL&Module& (16&Barrel,&2&Backward&ECAL) mass&4.9&tons Back&End&Board& (Services&32&FE&Boards) Roberto Petti USC
SiPM%reading%a%WLS%fiber Roberto Petti Front%End%Board% Back%End%Board% USC
Backup slides Roberto Petti USC
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