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Cir cular e+e- colliders to study THE BOSON X(126)

L E P 3. and TLEP. Cir cular e+e- colliders to study THE BOSON X(126). Strategic Questions: Now X(126) really exists ! A can LHC study X(126) and answer enough questions or do we need a complementary machine? shopping list :

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Cir cular e+e- colliders to study THE BOSON X(126)

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  1. LEP3 • and TLEP Circular e+e- collidersto study THE BOSON X(126)

  2. Strategic Questions: NowX(126) reallyexists! Acan LHC studyX(126) and answerenough questions or do weneed a complementary machine? shopping list: branching ratios, invisible width, exoticdecays mass, total width, spin-parity HH self couplings …… Bif yes, whatis really the complementary machine one needs? the redones are difficultat LHC… e+e- collider? Linear or circular?  collider?  collider

  3. What LHC can do is not fullyknown but a first glimpsewasgiven in the ALTLAS contribution to ESPP 2012

  4. Latestreference: The Higgsat LChas been studied for manyyears. Ata givenEcm and Luminosity, the physics case has marginally to do with the factthat the colliderislinear --specific: e- polarizationiseasyat the source, (not critical for Higgs) EM backgrounds frombeam disruption one IP seelater for precision on Higgs boson couplings and self couplings Difficulties: Linearcollideris know to beveryexpensive (15G$, 7G€) and very power-hungry(150-300MW istypicalbeam power consumption) evenatlowenergy Luminosityisdifficult to get (nm beam size, etc…)

  5. ATLAS indicated the possibility of ‘measuring’ (30%) the triple Higgscoupling by double Higgs production (HH ->  , bb) and the Httcoupling by means of ttH production. These are extremely important findings, as only a highenergy e+e- machine (the expensive one, Ecm> 500 GeV) can do this, and litteratureindicatesthatitdoes not do itbetter than ATLAS (15% on ttH and 20% on HHH) (ibid for mumu) ATLAS HL-LHC ttH ILC

  6. thisisverymuchlike VBF at LHC , e+ , Z,  , Z,  , e- e+e- collider

  7. Wyatt, Cracow

  8. Higgsphysicsat e+e- machine 240 ZH threshold tagged H, total width, invisible or exoticdecays, individualbranching ratios 350 tt threshold  measure top quark mass (input to EWRC measurements) 500 GeVttH  measurettHcoupling to 15% (> 500) HHH  measure HHH coupling to 20%, measureHvv production to (2%)  WHH coupling to 1% (but thatcouldbedonegivenenough ZH events) The really unique physicsseems to beat the ZH threshold (+ tt physicsat tt thresholdwouldbenice)

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

  10. 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 1034/cm2/s  20’000 HZ events per year. Z – tagging by missing mass e- H Z* Z e+ 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

  11. ILC Z – tagging by missing mass e- H Z* Z e+ total rate  gHZZ2 ZZZ final state  gHZZ4/ H  measure total widthH

  12. Genesis As the Higgsbecamecorneredbelow 140 GeV/c2 the question wasraised around the corridors ‘what about a new e+e- collidingring’ ? Raised the ‘LEP3’ at the EPS-HEP ECFA session in Grenoble (July 2011) and gotsuch feedback: (from ILC Higgs WG convener) the end? or the challenge?

  13. 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)  top-upbeamconsituouslywith a ancillaryaccelerator

  14. Extrapolatingfrom LEP2 LEP2: 104.5 GeV per beam luminositylifetime~200 minutes beampower was20MW * was 5cm and beam-beamtuneshift *was (asymptotically) ~0.12 RF frequency 352MHz  LEP2 was NOT at the beambeamlimit with*= 1mm, * =0.12 needshorterbunches, higherfrequency RF  ILC RF, 1.3 GHz ! OK  instantaneousluminosity100 times higher !  life time of O(minutes)! machine isunuseableunless … one refills all the time  B factory– like design; top off injection largeL dt (x5 w.r.t. LEP2) Atthatpoint Franck Zimmermanngotall excited, and quicklyconfirmed (3 days!) thathecouldapply the LHeCoptics to get the desiredresult! Telnov & Yokoyapointed out Beamstrahlung… requires 4% energy aperture obtained by increasing total RF volts from 8GV to 12 GV (cf ILC 250 GV) R.Assmann APAC 2011

  15. TLEP A long term vision… 80km tunnelaround Geneva couldbe fit avoiding Jura, Vuache and Salève… Then as a first step a « TLEP » 350 GeV e+e- ring couldbebuilt -- stillsignificantlycheaperthan the LC of the sameenergy -- reaching 175 GeV/beam (top threshold) with 6x1033 /cm2/s luminosity. The top thresholdisinteresting for precisionmeasurements of top mass, (rare) top decays and preciseconstraint on S This machine would have luminosityat ZH threshold of 5 1034/cm2/s x 2-4 IP’s thisis 40 times the linearcollider of the sameenergy. And as second step a new exploratory Hadron collider (80/27) * (20T/8T) * 14 TeV>80-100 TeVECM pp collider.

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

  17. PARAMETER LISTS

  18. Punchline: An e+e-storage ring collidercanbebuilt in the LEP/LHC tunnel whichwouldprovide 1034/cm2/s AverageLuminosity in 2/4 experiments i.e. 2/4x500fb-1 2/4x20’000 ZH events per year. In a larger tunnel (80km) a machine with 5times the performance these are 4 to 40 times the advertised ILC statisticsand reliable. Challenges: -- low vertical emittance must bemaintainedwhilefitting in the existing tunnel -- beam-beam interaction issomewhatextreme (but nothinglike LC!) -- Most components are ‘off-the-shelf’ exceptRF power source operating in CW mode -- first use of a large system of ILC cavities (8% of ILC@250 GeV) By-products -- By multibunching one wouldbe able to reachluminosities of O(~5 1035)/cm2/sat the Z pole (Tera-Z) O(~5 1034) /cm2/sat the W pair threshold (Mega W) MW < 1 MeV, MZ ,Z<< 1 MeV, sin2Weff <<0.0001 (to bestudied)

  19. 1989 The Number of light neutrinos isthis 2 effect an indication of massive sterile neutrinos? ALEPH+DELPHI+L3+OPAL in 2001 N = 2.984 0.008 Errordominated by systematics on luminosity.

  20. Azzi,etal.. Precisionmeasurements: once MHisknown (already125.60.5 GeV) all EW precisionmeasurementsbecome sensitive to WINP (WeaklyInteracting New Physics – by opposition to e.g. sterileneutrinos)

  21. The RF system The energy loss per turn of a single electron at 120GeV is 7GeV (3.5 GeV at LEP2) A good candidate for the RF system would be ILC-developed SC accelerating cavities at a frequency of 1.3 GHz RF and gradient of 18MV/m help reduce the bunch length, thus enabling a smaller y*. The total length of the RF system is therefore around 500m, similar to that of LEP2. Cryo power needed is less than half that of the LHC.

  22. Available 1.3 GHz klystrons J. Butterworth 1.3GHz ILC – FNAL-KEK (TH2104) Ucat/ Icat : 128kV/88A duty cycle: 2ms / 10Hz gain / η:50dB / 45% av. Power ≤ 200 kW Cost estimate: 240kEuros/tube 10MW 1.3GHz MBK – FLASH/XFEL Ucat/ Icat : 140kV/155A duty cycle: 1.5ms / 10Hz gain / η:50dB / 50% av. Power ≤ 150 kW Cost estimate: 400kEuros/tube THALES DESY DESY • Need to develop a klystron for CW operation • PCW ~450kW feasible?  2 cavities/klystron

  23. LHeC space considerations : LHeC : Space reserved for future e+e– machine The LHeC ring is displaced due to the requirement of keeping the same circumference as the LHC ring. LEP3 has no such requirement

  24. The low field dipoles (0.13 T) Another synergy with LHeC, although LEP3 wold require a “double decker” magnet LEP3 Artist’s impression BINP short model Prototypes of LHeC designs: Compact and lightweight to fit in the existing tunnel, yet mechanically stable CERN 400 mm long model

  25. Azzi, et al.. QUADS insertions in the CMS detector

  26. Experimental conditions -- Working group in CMS startedsomework on this.  luminosityisobtainedwithmany BB intereactions perfect for TPC or for CMS. Easier situation than ILC/CLIC  Beamstrahlung conditions and beam disruption are small  CM energyspreadis O(0.15%) (LC 2-5%)  Luminositymeasurement in order to reduce*y large aperture 17cm quads needed 4m from IP This requires minimum angle of 100mrad  1nb Bhabha cross section (was 30-120nb at LEP) but stillperfectlysufficient >108Bhabhas/year  Beam calibration: at the Z peak, beampolarizationshouldbe ‘easy’ for non collidingbunches (not known if polarization in collision canbedone) continuousenergy calibration for MZ ,Z measurements  athighenergy: beamenergyreproducibility  calibration on Z events or on resonantdepolarizationwith MeV precision (a weak point of LC)

  27. Azzi, et al.. Invisible, exotic and total widthmeasurementis the main selling argument for the e+e- machine difference: -- LC has only one IP, and 250fb-1 in 5 years @250 GeV ECM -- here simulation of CMS (a real detector) not LC detector

  28. Issues -- circular machine is not upgradable to higherenergies -- the choicereallydepends on LHC findings -- raised issue with the beamstrahlungreducing the life time (probelmsolved) -- LEP3 option for ATLAS and CMS? -- Linearcollider time scale = 2030. LEP3 couldbebeforethatbeforespoiling the HL-LHC -- impossible to runsimultaneously but interleaved running couldbeconsidered -- fitting LEP3 in LHC tunnel is not easy! -- TLEP is a superior machine (energy and luminosity) and not really more expensive – except for the 80km tunnel.

  29. Quite a few people findthat LEP3 isexciting! It provides an economical (or evenfeasible) solution to -- precisestudyof the X(126) propertieswhere LHC cannot do it -- and to performmanyprecisionmeasurements on H, W, Z (top) The machine is not ‘easy’ but shouldbe‘safe’ from the point of view of achieving the performance

  30. LEP3 2011 LEP3 on LI, 2012 BLEP2012 SuperTristan 2012 LEP3 in Texas, 2012 circular Higgs factories become popular around the world

  31. Nextevents: 1. Papersprepared for Europeanstrategy 2. local LEP3 workshop @ CERN on 23 October in IT auditorium. 3. ICFA beam dynamics workshop on "Accelerators for Higgs Factory: Linear vs. Circular" (HF2012) from November 14 to 16, 2012 at Fermilab. 4. if people interested in dedicated LEP3 WG please contact alain.blondel@cern.ch or frank.zimmermann@cern.ch (accelerator) 5. Wewouldlike to have two ATLAS contacts for the LEP3 study. (do not have to become aficionados!)

  32. Conclusions If the LHC measurements are not completeenough an lepton colliderwillbe necessary. In particularitis important to understandhow wellthe HH couplingcanbe addressedat LHC – itis not easyat the e+e- machine either! If itistruethat HL-LHC can do the HHH and ttHcouplingswellenough, the highenergy e+e- machine bringslittle to Higgsphysics Invisible width, total width, Hgg and Hcccanbedonemuchbetter with an e+e- colliderjustabove the ZH threshold (240 GeV) For thispurpose a ring e+e- collider LEP3 or TLEP canprovide an economicaland robust solution -- higherstatisticsthan LC and more than one IP. -- to study the X(125) withhighprecision -- and to performmanyprecisionmeasurements on H, W, Z (top) withinourlifetimes.

  33. LEP2/3 References: [1] A. Blondel, F. Zimmermann, ‘A High Luminosity e+e- Collider in the LHC tunnel to study the Higgs Boson,’ V2.1-V2.7, arXiv:1112.2518v1, 24.12.2011 [2] C. Adolphsen et al, ‘LHeC, A Large Hadron Electron Collider at CERN,’ LHeC working group, LHeC-Note-2011-001 GEN. [3] H. Schopper, The Lord of the Collider Rings at CERN 1980- 2000, Springer-Verlag Berlin Heidelberg 2009 [4] K. Oide, ‘SuperTRISTAN - A possibility of ring collider for Higgs factory,’ KEK Seminar, 13 February 2012 [5] R.W. Assmann, ‘LEP Operation and Performance with Electron-Positron Collisions at 209 GeV,’ presented at 11th Workshop of the LHC, Chamonix, France, 15 - 19 January 2001 [6] A. Butterworth et al, ‘The LEP2 superconducting RF system,’ NIMA Vol. 587, Issues 2-3, 2008, pp. 151 [7] K. Yokoya, P. Chen, CERN US PAS 1990, Lect.Notes Phys. 400 (1992) 415-445 [8] K. Yokoya, Nucl.Instrum.Meth. A251 (1986) 1 [9] K. Yokoya, ‘Scaling of High-Energy e+e- Ring Colliders,’ KEK Accelerator Seminar, 15.03.2012 [10] V. Telnov, ‘Restriction on the energy and luminosity of e+e- storage rings due to beamstrahlung,’ arXiv:1203.6563v, 29 March 2012 [11] H. Burkhardt, ‘Beam Lifetime and Beam Tails in LEP,’ CERN-SL-99-061-AP (1999) [12] R. Bossart et al, ‘The LEP Injector Linac,’ CERN-PS-90-56-LP (1990) [13] P. Collier and G. Roy, `Removal of the LEP Ramp Rate Limitation,’ SL-MD Note 195 (1995).

  34. HIGGS self-coupling This measurementwillbedifficultat all machines. itrequires a > 1TeV e+e- machine! It is crucial to understand if itcanbedoneat HL-LHC! or: isthere a precisionmeasurement or radiative correction thatcanbeused to constrainit? (CF WW couplingsfrom LEPI)

  35. Fabiola’s favorite: 125 GeVisreally a good place to be: bb , WW, gg, , ZZ, cc are all above a few % and  is ~maximal

  36. Questions: II ACCELERATOR Among the many questions that should be addressed in more detail: 1) a comparison of cost and performance for the proposed double ring separating the accelerator and collider and for a single combined ring; 2) a total of about 15 GV of RF acceleration is needed : 9 GV for the storage ring and 6 GV for the accelerator - it will be necessary to determine the optimum RF gradient as a compromise between cryopower and space requirement, and the optimum RF frequency with regard to impedance, RF efficiency and bunch length [in this paper we consider the use of high-frequency ILC-type cavities]; 3) the LHeC lattice has reduced the effective bending radius compared with LEP while one would rather like to increase it instead; 4) the performance may perhaps be further improved by using even smaller value of *y and e.g. the technique of crab waste-crossing[15]; 6) the performance at 91.2 Ecm(the Z peak), possibly with polarized beams 7) the co-habitation of such a double machine with the LHC would require careful examination of the layout of both machines - for the single LHeC ring no show-stopper has been found [7];

  37. 9) the ramping speed of the accelerator ring; 10) the positron source; 11) the limit on the single bunch charge; 12) the top-up scheme, e.g. injecting new bunches at full intensity or refilling those already colliding; and 13) the alternative possibility of building a new larger tunnel and storage ring(s) with thrice the LEP/LHC circumference, which we callTLEP. Possible TLEPparameters are listed in Table 2, alongside those for LEP3. Naturally, in the long-distant future a 3LEP tunnel could also house a proton collider ring with a beam energy about ten times higher than the LHC

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