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Higgs Factory Workshop Fermilab , 14-16 2012

Higgs Factory Workshop Fermilab , 14-16 2012. Physics session Warnings: 1 . Physics was not the primary goal of the workshop. 2. report precisions based on claimed performances 3. more extensive discussion on Higgs physics would be needed !. The Higgs Boson Discovery.

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Higgs Factory Workshop Fermilab , 14-16 2012

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  1. HiggsFactory Workshop Fermilab, 14-16 2012

  2. Physics session Warnings: 1. Physicswas not the primary goal of the workshop. 2. report precisionsbasedon claimedperformances 3. more extensive discussion on Higgsphysicswouldbe needed!

  3. The Higgs Boson Discovery 4th July 2012 Discovered Higgs-like Boson: Clear mass peak in gg and ZZ*4l Is this the SM one ? From searches to measurements CMS HCP CMS • observed: 6.9; expected: 7.8 3 F.Cerutti - Higgs Factory

  4. LHC has donebetterthanprojected: hereis a plot from ATLAS in 2005, expected~4with 10fb-1 at 14TeV • HCP 2012 (Kyoto): • -- mass (125.90.4 GeV/c2) (myaverage) • -- spin parity (0+ preferredat 2.45 -- CMS) alreadymeasuringcouplingsat20% level… (with a number of assuptions) gH-gluon =g gSMH-gluon fermion Vector boson Photon

  5. WhenmHisknownthe EW precisionmeasurements have no more freedom! • EW precisionmeasurements,rare decays(BS, etc… ) • -- 4th generation • -- SUSY • -- Higgs triplets • -- etc. etc. • Strongincentive to revisit and improve Z pole measurements and mW…

  6. The questions (Young-Kee-Kim): Is this the Standard Model Higgs? A Higgs beyond the SM? Measure the properties of this new particle with high precision yourBanker’s question: Whatprecisionisneeded to answer the question?

  7. Once the Higgs boson mass isknown, the Standard Model isentirelydefined. -- with the notable exception of neutrino masses, nature & mixings ***the only new physicsthereis*** but expectthese to be~ decoupledfromHiggsobservables (really?) 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? CP eigenstate? SM branching fractions to gauge bosons? Decays to new or invisible particles? All production modes as expected? Implications of MH ≈ 126 GeV? Any sign of new strong dynamics? yourBanker’s question: Whatprecisionisneeded to answer the question?

  8. The theorists (Chris Quigg) answer:

  9. Some guidance fromothertheorists R.S. Gupta, H. Rzehak, J.D. Wells, “How well do we need to measure Higgs boson couplings?”, arXiv:1206.3560 (2012) H. Baer et al., “Physics at the International Linear Collider”, in preparation, http://lcsim.org/papers/DBDPhysics.pdf • New physics affects the Higgs couplings • SUSY , for tanb = 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

  10. 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 significantsystematics in the production cross-sections prod Challenge willbe to constrainsystematics by measuringrelatedprocesses. if observed prod (gHi )2(gHf)2 extractcouplings to initial and final state H if i=f as in ZH with H ZZ  absolutenormalization

  11. Couplings at HL-LHC: ATLAS • MC Samples at 14 TeVfrom Fast-Sim. • Truth with smearing: best estimate of physics objects dependency onpile-up • Validated with full-sim. up to m~70 • Analyses included in ATLAS study: • Hgg0-jet and VBF • H  ttVBF lep-lep and lep-had • H  ZZ  4l • H WW  lnln0-jet and VBF • WH/ZH  gg • ttH gg (ttH mm) Direct top Y coupling • H  mm Second generation fermion coupling • HH bb ggHiggsSelf-Couplings ttH gg Very Robust channel Good S/B Statistically limited F.Cerutti - Higgs Factory

  12. Couplings fit at HL-LHC CMS • CMS Projection • AssumptionNO invisible/undetectable contribution to GH: • - Scenario 1: system./Theory err. unchangedw.r.t. current analysis • - Scenario 2: systematics scaled by 1/sqrt(L), theory errors scaled by ½ • ggloop at 2-5% level • down-type fermion couplings at 2-10%level • direct top coupling at 4-8% level • ggloop at 3-8% level F.Cerutti - Higgs Factory

  13. Conclusions 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, t, m 2-10% • ggandgg2-5% • HHH >3 s observation (2 Exper.) Assuming sizeable reduction of theory errors Approved LHC 300 fb-1 at 14 TeV: • Higgs mass at 100 MeV • Disentangle Spin 0vsSpin 2 andmain CP component in ZZ* • Coupling rel. precision/Exper. • Z, W, b, t 10-15% • t, m 3-2 sobservation • ggandgg 5-11% 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 F.Cerutti - Higgs Factory

  14. t gH 3% gH 3% H Full HL-LHC Z W b  

  15. HL-LHC ? ? ? i gHZgHbgHcgHggHWgH gH gH H H,inv

  16. HiggsFactoriesDreams

  17. S. Henderson

  18. Wyatt, Cracow

  19. Latestreference: The Higgsat a Linear e+e- Collider has been studied for manyyears Communityis large and wellorganized At a givenEcm and Luminosity, the physics has marginally to do with the factthat the colliderislinear --specifics: -+- e- polarizationiseasyat the source for ILC (not critical for Higgs) -- Beamenergy calibration at Z peak (perhaps WW) for rings -- EM backgrounds frombeamdisruption in Linear -- one IP in linear vs severalIps in circular.

  20. Higgs production mechanism In e+e– the Higgs is produced by “higgstrahlung” close to threshold Production xsection has maximum near threshold ~200 fb 1034/cm2/s  20’000 HZ events per year. H – tagging by missingmass to Z decay e- H Z* Z e+ For a Higgs of 125GeV, a centre of mass energy of ~240GeV is best  kinematical constraint near threshold for high precision in mass, width, selection purity

  21. ILC Z – tagging by missing mass total rate  gHZZ2 ZZZ final state  gHZZ4/ H  measure total widthH emptyrecoil = invisible width ‘funnyrecoil’ = exoticHiggsdecay easy control belowtheshold e- H Z* Z e+

  22. seealso M. Peskin, arXiv:1207.2516v1 (with th. assumptions) no HL-LHC ILC/CLIC 10 yearsatdesign luminosity

  23. t H Full HL-LHC Z W b  ILC : good! but not a radical improvement over HL-LHC can one do better? 

  24. What about a circular machine? LEP2 was not that far after all. One year of LEP2  ~200pb-1 x 4 exp. need 100fb-1! How can one increase over LEP 2 (average) luminosity by a factor 500 withoutexploding the power bill? Answeris in the B-factory design: a verylow vertical emittance ring with higherintrinsicluminosity electrons and positrons have a muchhigher chance of interacting  muchshorterlifetime (few minutes)  feedbeamcontinuouslywith a ancillaryaccelerator

  25. prefeasibilityassessment for an 80km projectat CERN John Osborne and Caroline Waiijer ESPP contr. 165

  26. LEP3, TLEP(e+e- -> ZH, e+e- →W+W-, e+e- →Z,[e+e-→t ) Zimmermann key parameters 10-40 times ILC lumi at ZH thresh. 2-8 times ILC lumi at ZH thresh. at the Z pole repeating LEP physics programme in a few minutes…

  27. gHZgHbgHcgHggHWgH gH gH H H,inv

  28. m+m-Collider vse+e-Collider ? • A m+m-collider can do things that an e+e-collider cannot do • Direct coupling to H expected to be larger by a factor mm/me • ,jh[speak = 70 pb at tree level] • Can it be built + beam energy spread dE/E be reduced to 3×10-5 ? • 4D+6D Coolingneeded! • For dE/E = 0.003% (dE~ 3.6 MeV, GH ~ 4 MeV) • no beamstrahlung, reduced bremsstrahlung • Corresponding luminosity ~ 1031 cm-2s-1 • Expect 2300 Higgs events in 100 pb-1/ year • Using g-2 precession, beam energy and energy spectrum • Can be measured with exquisite precision (<100 keV) • From the electrons of muon decays • Then measure the detailed lineshapeof the Higgs at √s ~ mH • Five-point scan, 50 + 100 + 200 + 100 + 50 pb-1 • Precision from H→bb and WW : [16,17] , W, … , W, … s (pb) √s s(mH), TLEP HF2012 : Higgs beyond LHC (Experiments)

  29. COOLING -- Principleisstraightforward… Longitudinal: Emittance exchange involvesionization varying in spacewhich cancels the dispersion of energies in the beam. This canbeused to reduce the energyspread and is of particularinterest for + -  H (125) since the Higgsisverynarrow (~4.2 MeV)

  30. COOLING -- Principleisstraightforward… Longitudinal: Transverse: Similar to radiation damping in an electronstorage ring: muon momentumisreduced in all directions by goingthroughliquidhydrogenabsorbers, and restoredlongitudinally by acceleration in RF cavities. Thus transverse emittance isreducedprogressively. Because of a) the production of muons by pion decay and b) the short muon lifetime, ionizationcoolingisonlypractical solution to producehighbrilliance muon beams Emittance exchange involvesionization varying in spacewhich cancels the dispersion of energies in the beam. This canbeused to reduce the energy spread and is of particularinterest for + -  H (125) since the Higgsisverynarrow (~5MeV) Practicalrealizationis not! MICE coolingchannel (4D cooling) 6D candidate coolinglattices

  31. CONCLUSIONS With the discovery of H(126) a new chapteris open in ParticlePhysics. It willtake a long time and shouldbeplannedcarefullywith an open mind. Chosingnow the wrong machine willkeep us for picking the right one in due time. HL-LHC willbealready an impressive HiggsFactory and the nextstepshouldmake large improvement over it. The circular e+e- Higgsfactories open veryinterestingpossibilities: -- LEP3 as a cheaperback-up to the ILC and -- TLEP as a superior, highprecisionHiggsfactory --with long term prospect towards a veryhighenergy hadron collider. now…. LET’S SEE WHAT THE ACCELERATORS CAN DO!

  32. BACK-UPS

  33. 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 report needed.

  34. Linear e+e Collider as a Higgs Factory • Advantages: • Extensive design and prototyping work have been done • Big investment have been made. Key technologies are in hand. • There exist well-organized international collaborations led respectively by the ILC GDE and CLIC Collaboration (to be combined under the Linear Collider Director appointed by ICFA) • Important steptowards high energye+e- collisions • Polarizedbeams (e- 80%, e+ 30%) • A front runner (in terms of readiness) • Challenges: • High cost • Specific issues: • ILC • FFS (goal emittance has not yet been achieved at ATF2) • Polarized Positron source works only for Ee- > 350GeV • Industrialization of SRF • For Higgs factory: Need 10 Hz for e+ production, or use unpolarized e+ beam as a backup scheme • CLIC • Accelerating structure • Industrialization of major components • From CDR to TDR

  35. Conclusions(2) • AlternateHiggsfactoriesconsideredinclude • -- circular e+e- collider • --  collider • --  collider • In combinationwith HL-LHC the physicscoverage of e+e- machines • isquitecomplete. • A  collideris a good add-on to linearcollider --one shoulddiscusscarefullywhatcanbedoneat  collider • thatcannotbedonebetween LHC and e+e- collider • --the claim of uniquenessis 2% resolution on  ; veryinteresting • A studydedicated to the understanding of the feasibility of the machine • and of the specificity of the measurementswouldbeworthwhile • A muon collidercould do everyting an e+e- could do if sameluminosity • canbereached. • --If an energyresolution of 0.003% canbeachieved (4D and 6D cooling!) • s-channelHiggs production allowssuperbmeasurements of the H(126) line shape and ‘fine structure’ exploration • -- A muon collideriscompletely unique to study the H/A system of • a Higgs doublet model • -- itremains the best way to reach>3 TeVenergy collisions between • point likeparticles.

  36. Conclusions(3) • -- e+e- ring collideroffera potentiallybetterluminosity/cost ratiothan the linearone and the possibility to have severalIPs. • -- 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 understandwhether the performance of circular machines couldbe as high as advertised • The answeris ‘maybe’ but thereislots of work to do to establishthis. • There are alsoideas to push the luminosityfurther. • This calls for a design study of circular e+e- HiggsFactory • -- If the luminositiesadvertisedcanbereached, the resolutions • on mostHiggscouplingscanbeimprovedfrom a few % to below percent precisions, opening the possibility of discovery of TeVscale new physics. • -- Revisiting Z pole and W thresholdisnow a must. This canbedoneatbothcircular and linear machines withsomedifferencesregardingenergy calibration and polarization.

  37. Extension possibilities • 1. LEP3 (C=27km) islimited to the ZH thresholdat 240 GeV • TLEP (C=80km) canreach 350 GeV. • all rings canaccept up to 4 collision pointsand runat the Z peak • 80km ring e+e- collider1st stepto O(100 TeV) pp collider • 400-500 GeVis the end limit to circular machines. • 2. linear machines canbeupgraded to energies up to ~1 or even 3 TeV • 3. the time structure isverydifferentbetweenlinear (pulsed) • and circular (CW) which has impact on the detector design. • The ILC detectors as presentlydesignedwould not work on a ring. • 4. A muon colliderremains the mostpromising option for the veryhigh • energy exploration with point-likeparticles.

  38. Conclusions -- The newlydiscoveredH(126) candidate is a fascinatingparticle of a new nature (elementaryscalar!) thatdeservesdetailedmeasurements -- There ismuch more to understand about Higgsphysicsmeasurements and theirpotential to test physicsbeyond the SM. This shouldbediscussed in a dedicated and detailedHiggsPhysics workshop. -- LHC is/willbean impressive Higgsfactory. This must betakenintoaccount in any future machine discussion! -- The linearcolliderILC canperformmeasurementsat few% level for the Higgs invisible width, search for exoticdecays, and improvement of bb, cc, W, Z couplingswrt LHC by factors2-5 -- 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 -- Nowthat the Higgs mass isknown, a new round of precision EWRC measurementsisstronglymotivated. (Predictedmtop, mHiggs, now sensitive inclusively to EW-coupled new physics)

  39. Higgs Physics with high-energy e+e- colliders 1. Similar precisions to the 250/350 GeV Higgs factory for W,Z,b,g,tau,charm, gamma and total and invisible width 2. ttHcoupling possible withsimilarprecision as HL-LHC (8-10%) 3. Higgs self couplingalsoverydifficult… precision 20-30% similar to HL-LHC I have to concludethat on the basis of the study of H(126) aloneisconcerned, the highenergy e+e- collideris not compelling Reversely, the Higgsphysicscanbedonewith CLIC athighenergy CLIC canworkat 250 GeVonwards – canitbebrought down to the Z pole?

  40. F.Cerutti - Higgs Factory Higgs boson production at LHC 8 TeV Theory systematics more relevant for ggH and ttH- Mass dependency very weak

  41. --Important measurementsatany moment depend on whatisalreadyknown What are the expectedprecisionsfrom HL-LHC? • -- mass (125.90.4 GeV/c2) (myaverage) • -- spin parity (0+ preferredat 2.45 -- CMS)  • Couplings : • -- H-Z and H-W (Vto ~20%) • -- H-t,b,c(f to ~20%) • -- H-,  • -- H-invisible (darkmatter candidates) • -- H-exotic • -- H-gluon,H- (20-30%) • -- H self coupling • -- CP violation • -- detailed line shape (more than one peaketc…) green = today black = HL-LHC red = no claim to be possible i = gimeas/giSM

  42. F.Cerutti - Higgs Factory Couplings at HL-LHC: ATLAS MC Samples at 14 TeVfrom Fast-Sim. Truth with smearing: best estimate of physics objects dependency onpile-up Validated with full-sim. up to m~70 Analyses included in ATLAS study: Hgg0-jet and VBF H  ttVBF lep-lep and lep-had H  ZZ  4l H WW  lnln0-jet and VBF WH/ZH  gg ttH gg (ttH mm) Direct top Y coupling H  mm Second generation fermion coupling HH bb ggHiggsSelf-Couplings ttH gg Very Robust channel Good S/B Statistically limited

  43. MICE Neutrino Factory MICEis one of the critical R&D experiments towards neutrino factories and muon colliders With the growing importance of neutrino physics + the existence of a light Higgs (125 GeV) physicscouldbeturningthiswayveryfast! Cooling and more generally the initial chain capture, buncher, phase rotation and cooling rely on complexbeamdynamics and technology, such as High gradient (~>16 MV/m) RF cavitiesembedded in strong (>2T) solenoidalmagneticfield MANY CHALLENGES! MUON COOLING  HIGH INTENSITY NEUTRINO FACTORY HIGH LUMINOSITY MUON COLLIDER

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

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