RAL seminar Alain Blondel Higgs Factory Workshop Fermilab, Nov.2012

The Higgs Boson Discovery 4 th July 2012 Discovered Higgs-like Boson: Clear mass peak in  and ZZ*  4 l Is this the SM one ? From searches to measurements 2 November/14/2012 F.Cerutti - Higgs Factory 2 CMS – observed: 6.9; expected: 7.8 CMS HCP Nov’12

RAL seminar Alain Blondel LHC has done better than projected: here is a plot from ATLAS in 2005, expected ~4  with 10fb-1 at 14TeV already measuring couplings at  20% level … (with a number of assuptions) g H-gluon =  g g SM H-gluon fermion Vector boson Photon HCP 2012 (Kyoto): -- mass (125.9  0.4 GeV/c 2 ) (my average) -- spin parity (0+ preferred at 2.45  -- CMS)

RAL seminar Alain Blondel When m H is known the EW precision measurements have no more freedom! EW precision measurements, rare decays (B S , etc… ) -- 4th generation -- SUSY -- Higgs triplets -- etc. etc. Strong incentive to revisit and improve Z pole measurements and m W …

RAL seminar Alain Blondel Is this the Standard Model Higgs? A Higgs beyond the SM? Measure the properties of this new particle with high precision The questions your Banker’s question: What precision is needed to see something interesting?

RAL seminar Alain Blondel Once the Higgs boson mass is known, the Standard Model is entirely defined. -- with the notable exception of neutrino masses, nature & mixings ***the only new physics there is*** but we expect these to be almost completely decoupled from Higgs observables. (true?) Does H(125.9) Fully accounts for EWSB (W, Z couplings)? Couples to fermions? Accounts for fermion masses? Fermion couplings ∝ masses? Are there others? Quantum numbers? SM branching fractions to gauge bosons? Decays to new particles? All production modes as expected? Implications of M H ≈ 126 GeV? Any sign of new strong dynamics? your Banker’s question: What precision is needed to see something interesting?

RAL seminar Alain Blondel Some guidance from theorists New physics affects the Higgs couplings SUSY, for tan  = 5 Composite Higgs Top partners Other models may give up to 5% deviations with respect to the Standard Model Sensitivity to “TeV” new physics needs per-cent to sub-per-cent accuracy on couplings for 5 sigma discovery LHC discoveries/(or not) at 13 TeV will be crucial to understand the strategy for future collider projects R.S. Gupta, H. Rzehak, J.D. Wells, “How well do we need to measure Higgs boson couplings?”, arXiv: (2012) H. Baer et al., “Physics at the International Linear Collider”, in preparation,

RAL seminar Alain Blondel The LHC is a Higgs Factory ! 1M Higgs already produced – more than most other Higgs factory projects. 15 Higgs bosons / minute – and more to come (gain factor 3 going to 13 TeV) Difficulties: several production mechanisms to disentangle and significant systematics in the production cross-sections  prod. Challenge will be to reduce systematics by measuring related processes.  i  f observed   prod (g Hi ) 2 (g Hf ) 2 extract couplings to anything you can see or produce from  H if i=f as in WZ with H  ZZ  absoulte normalization

Conclusions Approved LHC 300 fb -1 at 14 TeV: Higgs mass at 100 MeV Disentangle Spin 0 vs Spin 2 and main CP component in ZZ* Coupling rel. precision/Exper. Z, W, b,  10-15% t,  3-2  observation  and gg 5-11% 9 November/14/2012 F.Cerutti - Higgs Factory HL-LHC 3000 fb -1 at 14 TeV: Higgs mass at 50 MeV More precise studies of Higgs CP sector Couplings rel. precision/Exper. Z, W, b,  t,  2-10%  and gg 2-5% H  HH >3  observation (2 Exper.) Assuming sizeable reduction of theory errors LHC experiments entered the Higgs properties measurement era: this is just the beginning ! LHC Upgrade crucial step towards precision tests of the nature of the newly-discovered boson

Couplings at HL-LHC: ATLAS MC Samples at 14 TeV from Fast-Sim. Truth with smearing: best estimate of physics objects dependency on pile-up Validated with full-sim. up to  ~70 Analyses included in ATLAS study: H   0-jet and VBF H   VBF lep-lep and lep-had H  ZZ  4 l H  WW  l l 0-jet and VBF WH/ZH   ttH   ttH   Direct top Y coupling H   Second generation fermion coupling HH  bb  Higgs  Self-Couplings 10 ttH   November/14/2012 F.Cerutti - Higgs Factory Very Robust channel Good S/B Statistically limited

RAL seminar Alain Blondel HL-LHC will already be a Higgs factory, able to perform precise measurements on the relative values of the , gluon-gluon,  tt, bb, , , W and Z couplings. and even some hint (30% or 3  ) of Higgs self-coupling. Missing : absolute value of the Higgs total width (or overall strength of couplings) which could play against possible invisible or exotic decay mode in (fortuitous) cancellation. Precision not sufficient for sensitivity to TeV scale in Higgs couplings 2 values of expected errors: 1. assume same analysis and systematics 2. assume theory systematics will reduce by 2 and exp errors as 1/sqrt(N) recall :LEP reduced by factor 10 several theory systematics 2021

RAL seminar Alain Blondel b   Full HL-LHC Z W H t Relative

RAL seminar Alain Blondel

 collider

RAL seminar Alain Blondel

Patrick Janot      Collider vs e  e  Collider ?  A      collider can do things that an e  e  collider cannot do  Direct coupling to H expected to be larger by a factor m  /m e,jh [  peak = 70 pb at tree level]  Can it be built + beam energy spread  E/E be reduced to 3×10 -5 ? l 4D+6D Cooling needed! For  E/E = 0.003% (  E ~ 3.6 MeV,  H ~ 4 MeV) l no beamstrahlung, reduced bremsstrahlung è Corresponding luminosity ~ cm -2 s -1 Expect 2300 Higgs events in 100 pb -1 / year u Using g-2 precession, beam energy and energy spectrum l Can be measured with exquisite precision (<100 keV) è From the electrons of muon decays u Then measure the detailed lineshape of the Higgs at √s ~ m H l Five-point scan, pb -1 è Precision from H → bb and WW : 14 Nov 2012 HF2012 : Higgs beyond LHC (Experiments) 17  (m H ), TLEP, W, … mHmH  Peak HH 0.1 MeV0.6 pb0.2 MeV %5% √s  (pb) [16,17]

RAL seminar Alain Blondel Neutrino Factory MICE is one of the critical R&D experiments towards neutrino factories and muon colliders MICE MANY CHALLENGES! MUON COOLING  HIGH INTENSITY NEUTRINO FACTORY HIGH LUMINOSITY MUON COLLIDER With the growing importance of neutrino physics + the existence of a light Higgs (125 GeV) physics could be turning this way very fast! Cooling and more generally the initial chain capture, buncher, phase rotation and cooling rely on complex beam dynamics and technology, such as High gradient (~>16 MV/m) RF cavities embedded in strong (>2T) solenoidal magnetic field

HF2012 summary Physics-- Alain Blondel Fermilab Emittance exchange involves ionization varying in space which cancels the dispersion of energies in the beam. This can be used to reduce the energy spread and is of particular interest for  +  -  H (125) since the Higgs is very narrow (~4.2 MeV) COOLING -- Principle is straightforward… Longitudinal:

HF2012 summary Physics-- Alain Blondel Fermilab Similar to radiation damping in an electron storage ring: muon momentum is reduced in all directions by going through liquid hydrogen absorbers, and restored longitudinally by acceleration in RF cavities. Thus transverse emittance is reduced progressively. Because of a) the production of muons by pion decay and b) the short muon lifetime, ionization cooling is only practical solution to produce high brilliance muon beams Emittance exchange involves ionization varying in space which cancels the dispersion of energies in the beam. This can be used to reduce the energy spread and is of particular interest for  +  -  H (125) since the Higgs is very narrow (~5MeV) COOLING -- Principle is straightforward… Transverse: Longitudinal: Practical realization is not! MICE cooling channel (4D cooling) 6D candidate cooling lattices

RAL seminar Alain Blondel

The Higgs was barely missed at LEP2 LEP2: 26.7km circumference 4 IPs : L3, ALEPH, OPAL DELPHI 20MW of synchrotron radiation (scales as E 4 /R)  * = 5cm  luminosity lifetime ~ few hours L = /cm 2 /s H=20%; 240fb  50 Higgses per exp per year! able to do discovery, but not study! What else?

RAL seminar Alain Blondel ILC in a Nutshell Damping Rings Polarised electron source Polarised positron source Ring to Main Linac (RTML) (inc. bunch compressors) e- Main Linac Beam Delivery System (BDS) & physics detectors e+ Main Linac Beam dump not too scale

24 CLIC Layout at 3 TeV Drive Beam Generation Complex Main Beam Generation Complex 140  s train length - 24  24 sub-pulses 4.2 A GeV – 60 cm between bunches 240 ns 24 pulses – 101 A – 2.5 cm between bunches 240 ns 5.8  s Drive beam time structure - initial Drive beam time structure - final D. Schulte, CLIC, HF 2012, November 2012 Goal: Lepton energy frontier

RAL seminar Alain Blondel The Higgs at a Linear e+e- Collider has been studied for many years Community is large and well organized At a given Ecm and Luminosity, the physics has marginally to do with the fact that the collider is linear --specifics: e- (80%) and e+ (30%) polarization is easy at the source for ILC (not critical for Higgs) very small beams  very small beam pipe (b and c physics) pulsed at 5-10Hz  can pulse detector and save on cooling need (X0) Luminosity grows as E CM, /cm 2 /s at 500 GeV, one IP. cost grows as A+BE CM, both A and B are very large. ‘ready’. 10 years from approval to operation  start 2025… if all goes very well Latest reference:

RAL seminar Alain Blondel Higgs production mechanism Assuming that the Higgs is light, in an e + e – machine it is produced by the “higgstrahlung” process close to threshold Production xsection has a maximum at near threshold ~200 fb /cm 2 /s  20’000 HZ events per year. e+e+ e-e- Z* Z H For a Higgs of 125GeV, a centre of mass energy of 240GeV is sufficient  kinematical constraint near threshold for high precision in mass, width, selection purity Z – tagging by missing mass

27 best for tagged ZH physics: Ecm= m H +111  10 W. Lohmann et al LCWS/ILC2007 take 240 GeV.

RAL seminar Alain Blondel e+e+ e-e- Z* Z H Z – tagging by missing mass ILC total rate  g HZZ 2 ZZZ final state  g HZZ 4 /  H  measure total width  H empty recoil = invisible width ‘funny recoil’ = exotic Higgs decay easy control below theshold

29 New: 250 GeV (HZ) allows to disentangle ambiguity (intrinsic to LHC) between invisible width and total width +precision better to HL-LHC in bb and  cc high energy running allows Hvv channel +access to ttH and HHH… … not better than HL-LHC Can we get sub-% precision  sensitivity to TeV new physics?

RAL seminar Alain Blondel b   Full HL-LHC Z W H t

LEP3 day introduction -- Alain Blondel How can one increase over LEP 2 (average) luminosity by a factor 500 without exploding the power bill? Answer is in the B-factory design: a very low vertical emittance ring with higher intrinsic luminosity electrons and positrons have a much higher chance of interacting  much shorter lifetime (few minutes)  feed beam continuously with a ancillary accelerator

prefeasibility assessment for an 80km project at CERN John Osborne and Caroline Waiijer ESPP contr. 165

key parameters LEP3TLEP circumference26.7 km80 km max beam energy120 GeV175 GeV max no. of IPs44 luminosity at 350 GeV c.m.-0.7x10 34 cm -2 s -1 luminosity at 240 GeV c.m cm -2 s -1 5x10 34 cm -2 s -1 luminosity at 160 GeV c.m.5x10 34 cm -2 s x10 35 cm -2 s -1 luminosity at 90 GeV c.m.2x10 35 cm -2 s cm -2 s -1 at the Z pole repeating LEP physics programme in a few minutes… times ILC lumi at ZH thresh. 2-8 times ILC lumi at ZH thresh.

Proposal by K. Oide, 13 February 2012 SuperTRISTAN in Tsukuba: 40 km ring TLEP tunnel in the KEK area?

KEK 12.7 km 80 km ring in KEK area

105 km tunnel near FNAL H. Piekarz, “… and … path to the future of high energy particle physics,” JINST 4, P08007 (2009) (+ FNAL plan B from R. Talman)

What is a (CHF + SppC) Circular Higgs factory (phase I) + super pp collider (phase II) in the same tunnel e  e + Higgs Factory pp collider HF China Higgs Factory (CHF)

key parameters LEP3TLEP circumference26.7 km80 km max beam energy120 GeV175 GeV max no. of IPs44 luminosity at 350 GeV c.m.-0.7x10 34 cm -2 s -1 luminosity at 240 GeV c.m cm -2 s -1 5x10 34 cm -2 s -1 luminosity at 160 GeV c.m.5x10 34 cm -2 s x10 35 cm -2 s -1 luminosity at 90 GeV c.m.2x10 35 cm -2 s cm -2 s -1 at the Z pole repeating LEP physics programme in a few minutes… times ILC lumi at ZH thresh. 2-8 times ILC lumi at ZH thresh.

RAL seminar Alain Blondel Circular machine revisited after super-b and synchrotron light source: e.g. TLEP  sub % precision and sensitivity to TeV-scale physics.

RAL seminar Alain Blondel gHZ gHb gHc gHg gHW gH  gH  gH   H  H,inv

key parameters LEP3TLEP circumference26.7 km80 km max beam energy120 GeV175 GeV max no. of IPs44 luminosity at 350 GeV c.m.-0.7x10 34 cm -2 s -1 luminosity at 240 GeV c.m cm -2 s -1 5x10 34 cm -2 s -1 luminosity at 160 GeV c.m.5x10 34 cm -2 s x10 35 cm -2 s -1 luminosity at 90 GeV c.m.2x10 35 cm -2 s cm -2 s -1 at the Z pole repeating LEP physics programme in a few minutes…

Circular e + e  Collider as a Higgs Factory Advantages:  At 240 GeV, potentially a higher luminosity to cost ratio than a linear one  Based on mature technology and rich experience  Some designs can use existing tunnel and site  More than one IP  Tunnel of a large ring can be reused as a pp collider in the future Challenges:  Beamstrahlung limiting beam life time requires lattice with large momentum acceptance  RF and vacuum problem from synchrotron radiation  A lattice with low emittance  Efficiency of converting wall power to synchrotron radiation power  Limited energy reach  No comprehensive study; design study needed. 42 ICFA workshop on Higgs Factories, Fermilab November 2012

beamstrahlung: reducing  * and increasing current leads to radiation of particles in the field of the colliding bunch.  increase energy spread and produce tails LEP3 beamstrahlung more benign than for linear collider M. Zanetti (MIT) luminosity spectrum LEP3 & ILC:

RAL seminar Alain Blondel circular HFs – beamstrahlung  >2 s at  =1.0% (4 IPs)  >37 s at  =1.5%  >11 min at  =2.0%  >3h at  =2.5% simulation w 360M macroparticles  varies exponentially w energy acceptance  post-collision E tail → lifetime  TLEP at 240 GeV: M. Zanetti (MIT)  >6 s at  =2.0% (4 IPs)  >37 s at  =2.5%  >3 min at  =3.0%  >20 min at  =3.5% TLEP at 350 GeV:

RAL seminar Alain Blondel LEP3 (C=27km) is limited to the ZH threshold at 240 GeV + complicated (and unlikely) to integrate in the LHC tunnel  keep it as backup if all else fails 2. TLEP (C=80km) is the favorite: superb physics performance, revisit all EW energy scale GeV. with up to 4 collision points 80km ring e+e- collider can be 1st step to O(100 TeV) pp collider, and ~100GeV 50 TeV ep collider thereby offering long term vision at CERN 3. linear machines can be upgraded to energies up to ~1 or even 3 TeV (upgrade path from ILC to CLIC in same tunnel has been discussed) 4. A muon collider remains the most promising option for the very high energy exploration with point-like particles. Extension possibilities

RAL seminar Alain Blondel PSB PS (0.6 km) SPS (6.9 km) LHC (26.7 km) TLEP (80 km, e + e -, up to ~370 GeV c.m.) VHE-LHC (pp, up to 100 TeV c.m.) same detectors? also: e ± (100 GeV) – p (7 & 50 TeV) collisions possible long-term strategy ≥50 years of e + e -, pp, ep/A physics at highest energies (E. Meschi) Zimmermann

RAL seminar Alain Blondel all of this is for TLEP/VHE-LHC

RAL seminar Alain Blondel Conclusions -- The newly discovered H(126) candidate is a fascinating particle of a new nature (elementary scalar!) that deserves detailed measurements -- There is much more to understand about Higgs physics measurements and their potential to test physics beyond the SM. This should be discussed in a dedicated and detailed Higgs Physics workshop. -- LHC is/will be an impressive Higgs factory. This must be taken into account in any future machine discussion! -- The linear collider ILC can perform measurements at few% level for the Higgs invisible width, search for exotic decays, and improvement of bb, cc, couplings wrt LHC by factors ~2 -- for , , , ttH, HHH, HL-LHC will do ~ as well or better -- There is a strong motivation to investigate if one could do better -- more precise or/and cheaper -- Now that the Higgs mass is known, a new round of precision EWRC measurements is strongly motivated. (Predicted m top, m Higgs, now sensitive inclusively to EW-coupled new physics)

RAL seminar Alain Blondel e+e- ring collider offer a potentially better luminosity/cost ratio than the linear one and the possibility to have several IPs. -- Much progress has been brought about by the experience of LEP2 B factories and Synchrotron light sources. -- The main point of the HF2012 workshop was to understand whether the performance of circular machines could be as high as advertised The answer is ‘maybe’ but there is lots of work to do to establish this. There are also ideas to push the luminosity further. This calls for a design study of circular e+e- Higgs Factory -- If the luminosities advertised can be reached, the resolutions on several Higgs couplings can be improved from a few % to below percent precisions, opening the possibility of discovery of TeV scale new physics. -- Revisiting Z pole and W threshold is now a must. This can be done at both circular machines with extreme precision using the virtues of excellent calibration and polarization. Conclusions(2)

RAL seminar Alain Blondel

TLEP design study –preliminary structure for discussion PhysicsExperiments Accelerator 1. Theoretical implications and model building 2. Precision measurements, simulations and monte-carlos 3. Combination + complementarity with LHC and other machines ; global fits 1. H(126) properties 2. Precision EW measurements at the Z peak and W threshold 3. Top quark physics 4. Experimental environment 5. Detector design 6. Online and offline computing 1. Optics, low beta, alignment and feedbacks 2. Beam beam interaction 3. Magnets and vacuum 4. RF system 5. Injector system 6. Integration w/(SHE)-LHC 7. Interaction region 8. Polarization &E-calib. 9. Elements of costing Steering group web site, mailing lists, speakers board, etc.. International Advisory board Institutional board

RAL seminar Alain Blondel CONCLUSIONS(3) With the discovery of H(126) a new chapter is open in Particle physics. It will take a long time and should be planned carefully. Depending on the outcome of LHC run at 14 TeV, a dedicated machine to study with great precision the Electroweak scale GeV, will be very strongly motivated. An e+e- collider situated in a new 80km tunnel, offers outstanding luminosity and precision. It can serve as a precursor for a high energy exploratory pp machine at ~100 TeV There are many challenges! A design study has been recommended and you are very welcome to participate