LOW EMITTANCE MUON BEAMS FROM POSITRONS Francesco Collamati (INFN-Roma) 29.09.2017 1
Outline • Introduction: Why a muon collider • Proposal for a novel technique for direct muon production • Target choice & accelerator scheme • Multi-turn simulations • Muons’ emittance • Experimental tests • Conclusion and perspectives 2
Why a Muon Collider? 3
Why a Muon Collider? • PROs: 3
Why a Muon Collider? • PROs: • Muons are ~200 times heavier than electrons: 3
Why a Muon Collider? • PROs: • Muons are ~200 times heavier than electrons: • Accelerator : • No synchrotron radiation (limit of circular e + e - colliders) ➜ much higher energies are reachable (~3TeV in 4km circumference) 3
Why a Muon Collider? • PROs: • Muons are ~200 times heavier than electrons: • Accelerator : • No synchrotron radiation (limit of circular e + e - colliders) ➜ much higher energies are reachable (~3TeV in 4km circumference) • Much smaller energy spread of the beam ➜ much higher energy resolution • Precise measurements and access to new resonances 3
Why a Muon Collider? • PROs: • Muons are ~200 times heavier than electrons: • Accelerator : • No synchrotron radiation (limit of circular e + e - colliders) ➜ much higher energies are reachable (~3TeV in 4km circumference) • Much smaller energy spread of the beam ➜ much higher energy resolution • Precise measurements and access to new resonances • Physics : • Higgs coupling ∝ m 2 ➜ Much bigger production of Higgs boson (also s-channel) 3
Why a Muon Collider? 4
Why a Muon Collider? • CONs: 4
Why a Muon Collider? • CONs: • Muons decay in 2.2 μ s ! • The whole chain (generation, acceleration, interaction) must be very quick ! 4
Why a Muon Collider? • CONs: • Muons decay in 2.2 μ s ! • The whole chain (generation, acceleration, interaction) must be very quick ! • Traditional muon production scheme leads to large emittance beams: p + target ➝ π /K ➝ μ • Muons are produced with a variety of angles and energies (P μ ~100MeV/c) • Cooling needed! ➜ tradeoff monochromaticity/luminosity 4
Direct muon production N o v e l A p p r o a c h 5
Direct muon production N o v e l A p p r o a c h μ + ~22GeV Lab. Frame • Exploiting the interaction of accelerated positrons on fixed target: e + e − → µ + µ − θ μ e + e - 45GeV μ - ~22GeV 5
Direct muon production N o v e l A p p r o a c h μ + ~22GeV Lab. Frame • Exploiting the interaction of accelerated positrons on fixed target: e + e − → µ + µ − θ μ e + e - • Advantages: 45GeV μ - ~22GeV 5
Direct muon production N o v e l A p p r o a c h μ + ~22GeV Lab. Frame • Exploiting the interaction of accelerated positrons on fixed target: e + e − → µ + µ − θ μ e + e - • Advantages: 45GeV μ - • Low emittance possible: ~22GeV θ μ is tunable with √ s, and is very small close to the threshold 5
Direct muon production N o v e l A p p r o a c h μ + ~22GeV Lab. Frame • Exploiting the interaction of accelerated positrons on fixed target: e + e − → µ + µ − θ μ e + e - • Advantages: 45GeV μ - • Low emittance possible: ~22GeV θ μ is tunable with √ s, and is very small close to the threshold • Small energy spread : depends on √ s, small at threshold (210MeV) 5
Direct muon production N o v e l A p p r o a c h μ + ~22GeV Lab. Frame • Exploiting the interaction of accelerated positrons on fixed target: e + e − → µ + µ − θ μ e + e - • Advantages: 45GeV μ - • Low emittance possible: ~22GeV X COOLING θ μ is tunable with √ s, and is very small close to the threshold • Small energy spread : depends on √ s, small at threshold (210MeV) 5
Direct muon production N o v e l A p p r o a c h μ + ~22GeV Lab. Frame • Exploiting the interaction of accelerated positrons on fixed target: e + e − → µ + µ − θ μ e + e - • Advantages: 45GeV μ - • Low emittance possible: ~22GeV X COOLING θ μ is tunable with √ s, and is very small close to the threshold • Small energy spread : depends on √ s, small at threshold (210MeV) • Low background : low emittance allows for good luminosity with reduced muon flux • Reduced losses from decay: asymmetric collision allows high boost (and both muons’ collection) 5
Direct muon production N o v e l A p p r o a c h μ + ~22GeV Lab. Frame • Exploiting the interaction of accelerated positrons on fixed target: e + e − → µ + µ − θ μ e + e - • Advantages: 45GeV μ - • Low emittance possible: ~22GeV X COOLING θ μ is tunable with √ s, and is very small close to the threshold • Small energy spread : depends on √ s, small at threshold (210MeV) • Low background : low emittance allows for good luminosity with reduced muon flux • Reduced losses from decay: asymmetric collision allows high boost (and both muons’ collection) • Disadvantages: • Rate : much smaller cross section wrt protons ( μ b vs mb) 5
Direct muon production N o v e l A p p r o a c h mrad q µ max 2 1.6 s (e + e - à µ + µ - ) 1.2 0.8 r s µ b = 4 m e θ MAX 4 − m 2 0.4 µ µ s 1 0 0.8 44 46 48 50 52 54 56 58 60 E beam (e + ) GeV 0.6 0.4 0.2 r.m.s. ( E µ ) /E µ 0.3 0 0.25 44 46 48 50 52 54 56 58 60 E beam (e + ) GeV 0.2 0.15 √ s 0.1 r s 4 − m 2 ∆ E = 0.05 µ 2 m e 0 44 46 48 50 52 54 56 58 60 E beam (e + ) GeV 6
Target choice 7
Target choice • Due to low cross section, the target choice is crucial: N µµ = N e + ρ e − L σ ( e + e − → µ + µ − ) 7
Target choice • Due to low cross section, the target choice is crucial: N µµ = N e + ρ e − L σ ( e + e − → µ + µ − ) • Criteria: 7
Target choice • Due to low cross section, the target choice is crucial: µ +/- e + beam e + L N µµ = N e + ρ e − L σ ( e + e − → µ + µ − ) e + on • Criteria: target • ⬇ emittance ➜ thin target x’ x 1 ’ = x 0 ’ if L was a e + x drift x 1 = L x 0 ’ x 0 x 0 ’ x’ q µ max x ’ max = Muons produced µ +/ + / - - uniformly x max = L x ’ max along target 7
Target choice • Due to low cross section, the target choice is crucial: µ +/- e + beam e + L N µµ = N e + ρ e − L σ ( e + e − → µ + µ − ) e + on • Criteria: target • ⬇ emittance ➜ thin target x’ x 1 ’ = x 0 ’ • ⬆ rate ➜ high Z& ρ if L was a e + x drift x 1 = L x 0 ’ x 0 x 0 ’ x’ q µ max x ’ max = Muons produced µ +/ + / - - uniformly x max = L x ’ max along target 7
Target choice • Due to low cross section, the target choice is crucial: µ +/- e + beam e + L N µµ = N e + ρ e − L σ ( e + e − → µ + µ − ) e + on • Criteria: target • ⬇ emittance ➜ thin target x’ x 1 ’ = x 0 ’ • ⬆ rate ➜ high Z& ρ if L was a e + x drift x 1 = L x 0 ’ x 0 • ⬇ positron loss (brem.+bhabha) x 0 ’ (recirculation) ➜ low Z x’ q µ max x ’ max = Muons produced µ +/ + / - - uniformly x max = L x ’ max along target 7
Target choice • Due to low cross section, the target choice is crucial: µ +/- e + beam e + L N µµ = N e + ρ e − L σ ( e + e − → µ + µ − ) e + on • Criteria: target • ⬇ emittance ➜ thin target x’ x 1 ’ = x 0 ’ • ⬆ rate ➜ high Z& ρ if L was a e + x drift x 1 = L x 0 ’ x 0 • ⬇ positron loss (brem.+bhabha) x 0 ’ (recirculation) ➜ low Z x’ • Very intense e + source (10 18 e + /s @T) q µ max x ’ max = Muons produced µ +/ + / - - uniformly x max = L x ’ max along target 7
Target choice • Due to low cross section, the target choice is crucial: µ +/- e + beam e + L N µµ = N e + ρ e − L σ ( e + e − → µ + µ − ) e + on • Criteria: target • ⬇ emittance ➜ thin target x’ x 1 ’ = x 0 ’ • ⬆ rate ➜ high Z& ρ if L was a e + x drift x 1 = L x 0 ’ x 0 • ⬇ positron loss (brem.+bhabha) x 0 ’ (recirculation) ➜ low Z x’ • Very intense e + source (10 18 e + /s @T) q µ max x ’ max = Muons • Possible choices: produced µ +/ + / - - uniformly x max = L x ’ max along target 7
Target choice • Due to low cross section, the target choice is crucial: µ +/- e + beam e + L N µµ = N e + ρ e − L σ ( e + e − → µ + µ − ) e + on • Criteria: target • ⬇ emittance ➜ thin target x’ x 1 ’ = x 0 ’ • ⬆ rate ➜ high Z& ρ if L was a e + x drift x 1 = L x 0 ’ x 0 • ⬇ positron loss (brem.+bhabha) x 0 ’ (recirculation) ➜ low Z x’ • Very intense e + source (10 18 e + /s @T) q µ max x ’ max = Muons • Possible choices: produced µ +/ + / - - • Heavy materials (Cu…) ⇔ thin target ( ε μ ∝ L) uniformly x max = L x ’ max along Small ε μ , but high ρ brings to MS and e + loss • target 7
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