the ldmx experiment - agenda (indico)
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THE LDMX EXPERIMENTJEREMIAH MANS (University of Minnesota),
ON BEHALF OF THE LDMX TEAMOCTOBER 25, 2016
10/25/16 LDMX Experiment :: Mans 1
The Thermal Relic Target
𝑌~1
𝜎𝑣 &𝑚𝑀)*
The lowerthe mass,
the weaker the coupling!
• The measurements of the cosmic microwave background establish a matter-density target for dark matter.
• If the dark matter is produced thermally, the observed abundance sets a requirement for the ratio between coupling and particle mass.
10/25/16 LDMX Experiment :: Mans 2
WIMPs are dead, long live the LDM?• Various searches at the LHC are
excluding the most “naive” version of the WIMP miracle: a weak-scale-coupling which implies an ~100 GeV particle
• The lighter part of the phase space is much harder to access – the coupling must be much lower, which makes it difficult to produce in a collider
• Fixed-target configurations are likely the only way to get large-enough luminosities
10/25/16 LDMX Experiment :: Mans 3
RelicDens
ity
BaBar
LHC
LEP
E137
E787 E949
LSND
1 10 102 10310-1610-1510-1410-1310-1210-1110-1010-910-810-710-610-510-410-3
mχ (MeV)
y=ϵ2αD(m
χ/mA')4
Pseudo-Dirac Thermal Relic DM
Missing Momentum Concept
DM
DM
• Disappearance measurement: Use an electron beam on an active fixed target and identify events where momentum (energy) is lost
• Use of a moderate energy electron beam suppresses neutrino backgrounds compared with proton beams
First generation, fixed-target missing energy search : NA64
10/25/16 LDMX Experiment :: Mans 4
Cartoon Guide to LDMX
x ·
TaggingTracker
RecoilTracker
High-intensityelectron beam
Calorimeter
10% XoW target
l Signal definition is a low energy, moderate pTelectron and an otherwise empty calorimeter given a full-energy beam electron- Recoil pT between ~80 MeV and 800 MeV
- Backgrounds come from hard interactions in the target (e.g brehmstrahlung)- Several challenging backgrounds arise
when the forward photon has a photonuclear interaction
10/25/16 LDMX Experiment :: Mans 5
𝜸 + 𝒏 → 𝒏𝒏/𝒏𝜸 + 𝒑 → 𝝅2𝒏
𝜸 + 𝑵 → 𝑵𝝅2𝝅5
Requirementsl Dense, fast calorimeter able to
separate multiple showers to allow high-intensity beam- Must also be radiation-hard
l Incoming (tagger) tracking to pinpoint photon impact position, reject off-momentum incoming particles
l Outgoing (recoil) tracking to measure recoil electron, identify closely-spaced charged particles
l MIP-sensitivity in calorimeter to identify photonuclear processes
10/25/16 LDMX Experiment :: Mans 6
Beam requirements and concept
BSY dump
LDMX
Soft X-Ray FEL
Hard X-Ray FEL
Beam Kickers
LCLS-II SCRF Linac
FEL and DASEL bunches from RF gun
• To reach the thermal relic target, O(1015 – 1016) electrons-on-target are required, at a one (few) at-a-time rate: high charge, low current
• DASEL concept has been developed to produce such a beam using the LCLS-II Linacat SLAC in a parasitic mode of operation
• Beamline concept is achievable at moderate cost. Logistics of integration and installation are being evaluated by the accelerator experts at SLAC
10/25/16 LDMX Experiment :: Mans 7
The LDMX Detector Concept
10/25/16 LDMX Experiment :: Mans
■ Dual purpose Magnet and Tracking– Collimated precision tagger tracker in full field ® 10% XO target ® compact and precision
recoil tracker in fringe field
■ Si-W sampling calorimeter (ECAL)– 40 XO, 30 Layers, 7 modules per layer of high efficiency, high granularity calorimetry
■ Scintillator-Steel sampling calorimeter (HCAL) behind and around ECAL– 15 layers, un-segmented for simplicity : Veto any event with hadronic activity
8
Tracker designs based on HPS
APV25 hybrids
Front-endreadout boards
target
Silicon Sensors
• Tagging tracker: Tag incoming e-
• Precise p and (x,y) position at target.
• Recoil tracker: • Associate tag to recoil• Determine p after the
target down to 50 MeV
• Screen out straggling (off EBeam) electrons
• Measure Dp across target• The key discriminator
10/25/16 LDMX Experiment :: Mans 9
Tagging Tracker Recoil Tracker
Expected Tracker Performance
Acceptance
EfficiencyReconstructed 1.2 GeV e-’
Off-energy beam components are not
reconstructed into on-energy window (>3.5
GeV)
Position resolution at
target for matching to
recoil
10/25/16 LDMX Experiment :: Mans 10
ECAL Requirements
10/25/16 LDMX Experiment :: Mans 11
• LDMX ECAL is effectively the beam stop for the DASEL beamline
• High rate requirement (46 MHz particle rep rate)
• Significant radiation load for an active detector
• Proposed solution: adopt the technology chosen for an even more-extreme case (HL-LHC endcaps)
• Fast, granular detector with precise cluster-timing capabilities is ideal for high-luminosity fixed-target operation
CMS HL-LHC Endcap Calorimeter
HGCModuleComponentsandcompletedmodule
1.W-CuBaseplate
2.Gold/Kapton 3.Nominal128padsensor 4.PCB
Successful test beams FNAL CERN in 2016
• LDMX requires 210 modules=1% of CMS
• Absorber structure of LDMX optimized to suppress unmeasured photonuclear events
10/25/16 LDMX Experiment :: Mans 12
Recent Testbeam Results
10/25/16 LDMX Experiment :: Mans 13
Pedestal 120 GeV pions (non-showering)
x 8
Hadronic Veto Calorimeter
Ongoing optimization
studies
• Critical role is in the identification of neutron-containing backgrounds
• Technology concept is based on iron absorber and plastic scintillator read out using CMS Phase 1 SiPM-based electronics
• Ongoing optimization studies including a “surrounding” HCAL to catch large-angle (45) neutrons and catch wide-angle brehmstrahlung in the target
10/25/16 LDMX Experiment :: Mans 14
Calorimeter performanceStudied 3 GeV photon corresponding to ~ 3�109 EOT in GEANT4 simulations =>
~80k of these have photonuclear reactions, rest are easily vetoed By applying a cut of 0.15
MeV in deposited energy for the ECAL and 8 MIPs in the HCAL, we achieve a rejection factor of ~108
on these backgrounds
Additional design work going on for the hadron veto, as most remaining events have a leading neutron, often at large angle (>30°)
10/25/16 LDMX Experiment :: Mans 15
Target and TriggerPhysics trigger
• Energy sums performed using the first 16 layers of the calorimeter, combined with the input of the target scintillator
• Simulation indicates reduction factor of 2 x 10-5 possible with no inefficiency for signal
• DAQ requires a few x 10-4
10/25/16 LDMX Experiment :: Mans 16
Physics potential
Scalar Rel
ic Target
Fermion R
elic Target
BaBar
LHC
LEP
E787/949
PADME
LDMXPhase 2
(4 & 8 GeV)
VEPP-3
NA64
MMAPS
DarkLight
Belle II
LDMX, Ph
ase 1
1 10 102 10310-1610-1510-1410-1310-1210-1110-1010-910-810-710-610-510-4
m� (MeV)
y=�2�D(m
�/mA')4
Missing Mass/Momentum Experiments (Kinetic Mixing)
10/25/16 LDMX Experiment :: Mans 17
Project Status■ DASEL beamline design
is at an advanced stage– Project is being
discussed with DOE to allow installation of the DASEL beamline during the LCLS-II construction stop in 2019
■ LDMX experiment design process is making good progress
– Current studies are focused on identifying photonuclear backgrounds in the calorimeters and target
■ Construction schedule focused on 2020/21 operation
– Compatible with CMS endcap calorimeter construction schedule
10/25/16 LDMX Experiment :: Mans 18
ADDITIONAL MATERIAL
10/25/16 LDMX Experiment :: Mans 19
10/25/16 LDMX Experiment :: Mans 20
Parameter space plot with existing and planned experiments’ sensitivitiesfrom Dark Sectors 2016 community report (arXiv: 1608.08632)
10/25/16 LDMX Experiment :: Mans 21
Parameter space plot with existing and planned experiments’ sensitivitiesfrom Dark Sectors 2016 community report (arXiv: 1608.08632)
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