Future Linear Colliders Future Linear Colliders for Particle Physics for Particle Physics E. Adli, University of Oslo/CERN E. Adli, University of Oslo/CERN March 28, 2007 March 28, 2007
Starting point: LEP and LHC Starting point: LEP and LHC This decade: both LEP and LHC This decade: both LEP and LHC LEP : 1989 - 2000 LHC : 2007- � Why more colliders? Why more colliders? � � What will they look like? What will they look like? �
Part I Part I A Future Linear Collider – – Why and How Why and How A Future Linear Collider
The three main parameters The three main parameters Accelerators for Particle Physics are characterized by: Accelerators for Particle Physics are characterized by: LEP LEP LHC LHC and e p, ions ( ions ( Pb, Au ) e + + and Pb, Au ) Particle type(s) e - - Particle type(s) e p, 209 GeV (max) (max) p: 14 TeV 14 TeV at p at p (~ 2- -3 TeV 3 TeV p: (~ 2 Collision energy (E cm ) Collision energy (E cm ) 209 GeV mass reach, depending mass reach, depending on physics) on physics) Pb: 1150 TeV Pb: 1150 TeV ) L ) 32 cm 34 cm Luminosity ( L Peak: 10 Peak: 10 Peak: Peak: 10 32 cm - -2 2 s s - -1 1 10 34 cm - -2 2 s s - -1 1 Luminosity ( Daily avg last years: (IP1 / IP5) Daily avg last years: (IP1 / IP5) 31 cm 10 31 cm - -2 2 s s - -1 1 10 Integrated: ~ 1000 pb - -1 1 Integrated: ~ 1000 pb (per experiment) (per experiment)
Particle type Particle type
Hadron versus lepton collisions Hadron versus lepton collisions � Can be elementary particle (lepton) or composite object Can be elementary particle (lepton) or composite object � (hadron) (hadron) - (lepton) � LEP: e LEP: e + + e e - (lepton) � � LHC: pp LHC: pp (hadron) (hadron) � � Hadron collider: Hadron collider: � � Hadrons easier to accelerate to high energies Hadrons easier to accelerate to high energies � ⇒ intrinsic parton energy spread ⇒ large Parton collisions ⇒ intrinsic parton energy spread ⇒ � Parton collisions large � discovery range discovery range � Lepton collider (LC): Lepton collider (LC): � � well well- -defined E defined E CM � CM � well well- -defined polarization (potentially) defined polarization (potentially) � -> > data analysis are in many caser simpler data analysis are in many caser simpler (single events can (single events can - be readily analyzed) be readily analyzed) -> are better at > are better at precision measurements precision measurements of many parameters of many parameters -
LHC and LC synergies: Higgs LHC and LC synergies: Higgs � LHC might discover one, or more, Higgs LHC might discover one, or more, Higgs � particles, with a certain mass particles, with a certain mass � However, discovery and mass is not enough However, discovery and mass is not enough � � Are we 100% sure it is really a SM/MSSM Higgs Are we 100% sure it is really a SM/MSSM Higgs � Boson? Boson? � What is its spin? What is its spin? � � Exact coupling to fermions and gauge bosons? Exact coupling to fermions and gauge bosons? � � What are its self What are its self- -couplings? couplings? � � So, are these properties exactly compatible with So, are these properties exactly compatible with � the SM/MSSM Higgs? the SM/MSSM Higgs? Confidence requires a need for precision Confidence requires a need for precision
Higgs: Spin Measurement Higgs: Spin Measurement � The SM Higgs must The SM Higgs must � have spin 0 have spin 0 � In a lepton collider we In a lepton collider we � will know E cm will know E cm � A lepton collider can A lepton collider can � measure the spin of any measure the spin of any Higgs it can produce Higgs it can produce e + e – → HZ (mH=120 GeV, 20 fb–1 ) Slide: B. Barish
Higgs: fermion couplings Higgs: fermion couplings � SM predicts g SM predicts g Hff / g Hf'f' = m f / m f' Hff / g Hf'f' = m f / m � f' ⇒ need Must be checked for all particle species ⇒ � Must be checked for all particle species need � μ + μ − > μ + μ − to measure also rare decays like H - -> to measure also rare decays like H � Some couplings might be measured by LHC Some couplings might be measured by LHC � � But sufficient But sufficient precision precision can only be reached in a can only be reached in a � lepton collider lepton collider
Higgs: self- -couplings couplings Higgs: self The Higgs potential (M&S notation): α λ HHH α λ � SM predicts g SM predicts g HHH � � Can be measured with polarized lepton collision via Can be measured with polarized lepton collision via � − − −> > HH Ζ + e e + e − HH Ζ e (Graph: M.M.Mühlleitner)
SUSY SUSY � if (SUSY) LHC will most probably detect a large if (SUSY) LHC will most probably detect a large � subset of sparticles, but might also miss a set subset of sparticles, but might also miss a set (depending on energy) (depending on energy) � A multi A multi- -TeV LC will TeV LC will � complement the LHC complement the LHC spectrum of discoveries spectrum of discoveries � LHC better LHC better squark squark- - � detection and a lepton detection and a lepton collider better slepton slepton- - collider better detection detection
Extra dimensions Extra dimensions � Applicable for both LHC and LC, but Applicable for both LHC and LC, but exact D exact D is is � easier to deduct with LC easier to deduct with LC Linear collider "New space-time dimensions can be mapped by studying the emission of gravitons into the extra dimensions, together with a photon or jets emitted into the normal dimensions" Slide: B. Barish
The Chainsaw and the Scalpel The Chainsaw and the Scalpel Lepton collider Lepton collider LHC LHC LHC + LC = SYNERGY
Collision energy Collision energy
Limitations LEP and LHC Limitations LEP and LHC We want E cm as high as possible for new particle accelerators We want E cm as high as possible for new particle accelerators � � ⇒ particles bended ⇒ two limitations occurs: circular colliders ⇒ particles bended ⇒ circular colliders two limitations occurs: � � I) synchrotron radiation energy loss I) synchrotron radiation energy loss P ∝ ∝ E 4 ⇒ ⇒ Limited LEP to E E 4 =209 GeV (RF energy replenishment) P cm =209 GeV (RF energy replenishment) Limited LEP to E cm ∝ m ⇒ changing to p in LHC ⇒ ⇒ P no longer the limiting factor P ∝ m 0 0- -4 4 ⇒ changing to p in LHC P P no longer the limiting factor II) Magnetic rigidity II) Magnetic rigidity p ρ = B e Technological limit of bending magnet field strength Technological limit of bending magnet field strength ⇒ Limits LHC to E ∝ B ) ⇒ =14 TeV ( ( ∝ B ) Limits LHC to E cm cm =14 TeV ⇒ Superconducting magnets needed ⇒ Superconducting magnets needed
Synchrotron radiation energy loss Synchrotron radiation energy loss � Main problem LEP: synchrotron radiation loss: Main problem LEP: synchrotron radiation loss: � � Though Though- -experiment: we want P experiment: we want P s =P LEP and E cm =2 TeV. s =P LEP and E cm =2 TeV. � What options do we have? What options do we have?
Option 1 Option 1 ⇒ R=2700 km (!) e, ⇒ � If we keep m=m If we keep m=m e, R=2700 km (!) � + synchrotron at this energy If we insist on an e - - e e + � If we insist on an e synchrotron at this energy � with LEP's LEP's power consumption the size will power consumption the size will with ridicoulous ridicoulous � ⇒ ⇒ NOT feasible NOT feasible , neither economically, , neither economically, � practically nor “ “culturally culturally” ” practically nor
Option 2 Option 2 u, ⇒ ⇒ R ~ 100 m (not the limiting factor anymore) Other idea: m=m u, R ~ 100 m (not the limiting factor anymore) Other idea: m=m � � a Muon Collider a Muon Collider Gives basically the same physics as an electron collider for the same same Gives basically the same physics as an electron collider for the � � E E CM CM , without the radiation loss , without the radiation loss τ u Only a small catch: τ =2.10 - -6 6 s Only a small catch: u =2.10 s � � τ LAB =0.5 TeV τ Time- -dilation helps a little bit, e.g. at E dilation helps a little bit, e.g. at E u =1.10 - -2 2 s s Time u =0.5 TeV LAB =1.10 � � ⇒ but we still have to accelerate and collide VERY fast ⇒ but we still have to accelerate and collide VERY fast In addition: problems with neutrino radiation In addition: problems with neutrino radiation serious studies has been done, but NOT feasible with today’ ’s technology s technology serious studies has been done, but NOT feasible with today � �
Option 3 Option 3 → ∞ ∞ but let R → � We go back to: m=m We go back to: m=m e, e, but let R � � Forget bending all together, accelerate along a Forget bending all together, accelerate along a � linear accelerator linear accelerator � Today: the Today: the ONLY feasible ONLY feasible way to do TeV way to do TeV- -scale scale � lepton- -lepton collisions lepton collisions lepton
Luminosity Luminosity
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