1 Muon Collider R & D : GeV Higgs Factory and beyond ? David Neuffer March 2013

2Outline  Introduction  Motivation  Scenario Outline and Features  Based on Fermilab MAP program~  Parameters - cooling  Proton Driver, Front End, Accelerator, Collider Features-spin precession energy measurement  Upgrade Path(s)  to High-Energy High Luminosity Muon Collider

126 GeV Higgs !  Low Mass Higgs ?  Observed at ATLAS-CMS ~126GeV ~”5+σ”  cross-section H   larger than MSM ~<2× in LHC measurement  a bit “beyond standard model” ? 3

126 GeV Significance  Higgs is fundamental source of mass (?)  interaction with leptons  Does Higgs exactly follow minimal standard model?  h – μ is simplest case 4

Higgs “ Factory ” Alternatives  Need Further exploration of 126 GeV  Study properties; search for new physics  Possible Approaches: 1.LHC  “high luminosity” LHC 2.Circular e + e - Colliders  LEP3, TLeP, FNAL site-filler, …  e + -e -  H + Z 3.Linear e + e - Colliders  ILC, CLIC, NLC, JLC  Plasma/laser wakefields/ 4.γγ Colliders 5.μ + -μ - Colliders  only s-channel source - μ + -μ -  H  precision energy measurement 5

Muon Accelerator Program ( MAP ) overview 6 LEP Collider 100x100 GeV A 4 TeV Muon Collider would fit on the Fermilab Site  =  s (0.08s)

MAP program - neutrinos  Neutrino oscillations mix all 3 known neutrino types  ν e, ν μ,ν τ + evidence for additional sterile neutrino states  Present ν beams are π decay:  π  μ +ν μ  Future beams will use μ decay:  μ  e+ν μ +ν e  Intense muon source  “Neutrino Factory” NuSTORM 7

Fermilab Muon Program  2 Major Muon experiments at Fermilab  mu2e experiment  g-2 experiment 3.1 GeV μ decay 8 μ2e Hall g-2 Hall

Muon Collider as a Higgs Factory Advantages:  Large cross section σ ( μ + μ - → h) = 41 pb in s-channel resonance( compared to e + e - → ZH at 0.2 pb)  Small size footprint, No synchrotron radiation problem, No beamstrahlung problem  Unique way for direct measurement of the Higgs line shape and total decay width   Exquisite energy calibration  A path to very high energy lepton-lepton collisions Challenges:  Muon 4D and 6D cooling needs to be demonstrated  Need small c.o.m energy spread (0.003%)  RF in a strong magnetic field  Background from constant muon decay  Significant R&D required towards end-to-end design  Cost unknown 9 s-channel production of Higgs boson s-channel Higgs production is 40,000 times larger than in an e + e  collider Muon collider can measure the decay width  directly (a unique advantage) – if the muon beam energy resolution is sufficiently high small energy spread feasible in ionization cooling

μμ  H Higgs Factory Barger, Berger, Gunion, Han, μμ  H Higgs Factory Barger, Berger, Gunion, Han, Physics Reports 286, 1-51 (1997)  Higgs Factory = s-channel resonance production  μ + μ -  H  Cross section expected to be ~50pb    m  2 = m e 2  width ~4MeV  at L=10 31, t=10 7 s  5000 H  Could scan over peak to get M H, δE H  b ̅ b or W + W - * mostly 10 δE = % =4 MeV ~10 36 /pt e + e × 10 -9

μ + μ - Collider Parameters  0.1~  0.4  3 + TeV Collisions  Parameters from 2003 STAB (+ Snowmass 2001) C. Ankenbrandt et al., Physical Review STAB 2, (1999), M. Alsharo’a et al., Physical Review STAB 6, (2003). 11  0.125

μ + - μ - Higgs Collider Design  Based on “3 TeV” μ + -μ - Collider design  scaling back cooling system; acceleration, collider ring  126 GeV precision Higgs measurements could be done as initial part of HE μ + -μ - Collider program … follow-up to LHC/LC programs ?  4 MW proton driver, solenoid target and capture, ionization cooling system, acceleration and collider ring  plus polarization precession for energy measurement at  ~10—20% polarization precession  Is there a “fast-track” path to the μ + -μ - Higgs ? 12

Cooling Constraints  Cooling method is ionization cooling  energy loss in material compensated by rf  opposed by d /ds, d /ds  Cooling couples x, y, z  At moderate B, E RF, RF, optimal 6-D cooling 13

Natural 6- D muon cooling limits  є T = ~0.0003m,є L = ~0.0015m  σ E = 3MeV  σ z =0.05m  Cooling to smaller є T requires “extensions ”  reverse є exchange  high B-fields, extreme rf, small E   Initial derated values  є T = m, є L = 0.002m 14  Ionization cooling couples x, y, z  At moderate B, E RF, RF, optimal 6-D cooling is:

GeV μ + - μ - Collider  8 GeV, 4MW Proton Source  15 Hz, 4 bunches 5×10 13 /bunch  π  μ collection, bunching, cooling  ε ,N =400 π mm-mrad, ε ‖,N = 2 π mm  / bunch  Accelerate, Collider ring   E = 4 MeV, C=300m  Detector  monitor polarization precession  for energy measurement  E error  0.1 MeV

Project X Upgrade to 4 MW  Upgrade cw Linac to 5ma  15 MW peak power  run at 10% duty cycle  Increase pulsed linac duty cycle to ~10%  8GeV × 5ma × 10% = 4MW  Run at 15 Hz (6.7ms injection/cycle)  matches NF/MC scenarios  Chop at 50% for bunching  source/RFQ  10ma  Need Accumulator, Compressor to bunch beam  + bunch combiner “trombone” 16

Alternative “ Low - Budget ” Proton driver ?  Proton driver delayed …  many stage f scenario 20+ year ….  Is there a shorter path from X1 to  Higgs?  2MW Main Injector? 60GeV – 1.5Hz, ~10 14 /pulse divide into 10 bunches ~15 Hz, p, 1m  3MW 3GeV buncher at 3 GeV 17

18 Solenoid lens capture  Target is immersed in high field solenoid  Particles are trapped in Larmor orbits  B= 20T -> ~2T  Particles with p  < 0.3 B sol R sol /2=0.225GeV/c are trapped  π  μ  Focuses both + and – particles  Drift, Bunch and “high-frequency” phase-energy rotation 

19 High - frequency Buncher and φ - E Rotator  Drift (π → μ), “Adiabatically” bunch beam first (weak 320 to 240 MHz rf)  Φ-E rotate bunches – align bunches to ~equal energies  240to 202 MHz, 15 MV / m  Cool beam MHz  Captures both μ + and μ -  born from same proton bunch 10 m~50 m FE Targ et Solenoid DriftBuncherRotatorCooler ~30m36m ~80 m p π→μ

 Capture / Buncher /  - E Rotation  Alternatives/variations should be explored  200 MHz  325 ?  shorter (lower cost versions)  improve initial cooling  Advantages  high rf frequency (200 MHz)  captures both signs  high-efficiency capture  Obtains ~0.1 μ/p 8  Choose best 12 bunches ~0.01 μ/p 8 per bunch  Disadvantages  requires initial protons in a few short, intense bunches  train of  bunches (not single) requires later recombiner  low polarization % 20

Cooling Scenario for 126 GeV Higgs  Use much of baseline cooling scenarios  need initial 200/400 Mhz cooling sections  need bunch merge  and initial recooler  Do not need final cooling (high field section)  final transverse cooling sections for luminosity upgrade  high-field cooling not needed (B < ~12T)  Cooling to smaller 21

Acceleration - scenario  Use Neutrino Factory Acceleration scenario; extend to 63 GeV  linac + Recirculating linacs  (“dogbone” accelerators)  small longitudinal emittance makes acceleration much easier higher-frequency rf 400/600 MHz 22 63GeV Collider Ring  E/2  E 8  63 2828 2

Acceleration Scenario ( Lebedev ) 23 3 GeV Linac 650 MHz SRF ~5 GeV Recirculating Linac 650 MHz ~12 turns to 63 GeV Linac + ~10 Pass Recirculating Linac to 63 GeV 5-6 GeV pulsed SRF Linac (650 MHz) “Dog-bone” recirculation same Linac can also be used for 3  8 GeV Project X stage 3 4MW for protons ?

24 Collider Ring (1999)  1 bunches of μ + and μ - (50x50)  2×10 12 μ/bunch  β* = 10 cm  4cm  σ= 0.04cm  β max = 600m  2000m  σ=3cm  IR quads are large aperture (25cm radius)  used ε L =0.012 eV-s (0.0036m)  (larger than expected cooled value)  δE ~0.003 GeV if σ z = 12cm (0.4ns)  δE/E <  Collider is not beam-beam limited  r  =1.36* m  Δν=0.002 R=33m at B ave = 6T Johnstone, Wan, Garren PAC 1999, p. 3066

Updated 63 x 63 GeV Lattice 25 Y. Alexahin C=300m Y. Alexahin

Beam Instability Issues  Studied in some detail by K.Y Ng  PhysRevSTAB 2, (1999) “Beam Instability Issues of the 50x50 GeV Muon Collider Ring”  Potential well distortion compensated by rf cavities  Longitudinal microwave instability ~isochronous lattice, small lifetime  Transverse microwave Instability damped by chromaticity (+ octupoles)  Beam Breakup BNS + δν damping  Dynamic aperture  larger than physical Y. Alexahin 26

Scale of facility 27 RLA Collider Ring Cooling line Proton Ring Linac Target +  Capture

Losses / Background  Major Problem is μ-decay  electrons from decay in detectors  also beam halo control  Collimation  remove beam halo by absorbers in straight section (opposite IR) Drozhdin, Mokhov et al. 28

126 GeV Detector  μ-Decay Background reduced by “traveling gate trigger” Raja -Telluride  Detector active for 2 ns gate from bunch collision time  H  b b*  forward cone ~10º absorber W absorber 29

Polarization & Energy measurement Raja and Tollestrup (1998) Phys. Rev. D  Electron energy (from decay) depends on polarization  polarization is ~25%  10%  Measure ω from fluctuations in electron decay energies 10 6 decays/m depends on Frequency  Frequencies can be measured very precisely  E, δE to 0.1 MeV or better (?)  need only > ~5% polarization ? 30

Polarization  Because the absolute value of the polarization is not relevant, and only frequencies are involved, the systematic errors are very small (~5-100 keV) on both the beam energy and energy spread.  A. Blondel 31

μ + μ -  Z (90 GeV ) = “ Training Wheels ”  Run on Z until luminosity established  easier starting point  σ = ~30000 pb 3000 Z/day at L=10 30  Debug L, detectors, background suppression, spin precession, at manageable parameters  Useful Physics at Z ? E, ΔE to ~0.1 MeV or less μ + μ -  Z 0  Then move up to 125 GeV energy sweep to identify H δE ~ 10MeV  3MeV 32

Higgs MC Parameters - Upgrade ParameterSymbolValue Proton Beam PowerPpPp 4 MW Bunch frequencyFpFp 15 Hz Protons per bunchNpNp 4×5×10 13 Proton beam energyEpEp 8 GeV Number of muon bunchesnBnB 1  +/- / bunch NN 5×10 12 Transverse emittance  t,N m Collision  * ** 0.05m Collision  max ** 1000m Beam size at collision  x,y nm Beam size (arcs)  x,y 0.3cm Beam size IR quad  max 4cm Collision Beam EnergyE  +,E  _ 62.5(125geV total) Storage turnsNtNt 1300 LuminosityL0L Proton Linac 8 GeV Accumulator, Buncher Hg target Linac RLAs Collider Ring Drift, Bunch, Cool Reduce transverse emittance to m More Protons/pulse (15 Hz) δν BB =  1 bunch combiner H/yr

Upgrade to higher L, Energy  higher precision  More acceleration  top mass measurement at 175 GeV  extended Higgs  A, H at 500 GeV ?  larger cross sections  larger energy widths  TeV new physics ? 34 T. Han & S. Liu

Initial scenario possibilities ( Nov. HFWS )  start with luminosity?  measure m H, δm H  Fewer protons?  ~1—2MW source  Less cooling?  leave out bunch recombiner  ~ m path length  Need to validate cooling, polarization energy measurement  Muon Higgs workshop  UCLA – ~March 20 35

36 Upgrade path ( E and L )  More cooling  ε t,N → , β * →1cm  Bunch recombination  60Hz  15 ?  L →10 32  More cooling  low emittance  ε t,N → , β * →0.3cm  L →10 33  More Protons  4 MW  8  ?  15Hz  L →10 34  more Acceleration  4 TeV or more …  L →10 35

Comments  GeV Higgs is not easy  small cross section, small width  Need high-luminosity (> ~10 30 cm -2 s -1 )  Need high-intensity proton Driver N MW, 5—50 GeV, pulsed mode (10—60 Hz )  Need MW target, π  μ collection  Need ionization cooling by large factors ε t : 0.02  m; ε L : 0.4  m.  acceleration, collider ring, detector spin precession energy measurement  can get precision energy and width  Not extremely cheap  Most of the technology that we need for high-L high-E μμ Collider 37

Professional endorsements 38

Start with light muons GeV e + - e - Collider  No direct H production in e + -e -  No narrow resonance associated production Z +H  e + -e -  ZH  ~0.2pb at 250GeV background is ~10pb  200/year at L =10 32 (~LEP)  20000/year at L = pb e + -e -  ZH  l + l - H 1500 “high-quality” events  Z + H not as cleanly separated from background  H width cannot be resolved  But do not have to sit on resonance to see H 39