higgs factory workshop fermilab , 14-16 nov.2012

RAL seminar Alain Blondel 13-02-2013

Higgs Factory Workshop Fermilab, 14-16 Nov.2012

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 measurements2November/14/2012 F.Cerutti - Higgs Factory

2

CMS

– observed: 6.9; expected: 7.8

CMSHCP

Nov’12


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)

gH-gluon =ggSM H-gluon

fermion

Vector bosonPhoton

HCP 2012 (Kyoto):-- mass (125.90.4 GeV/c2) (my average)-- spin parity (0+ preferred at 2.45 -- CMS)


When mH is known the EW precision measurements have no more freedom!

EW precision measurements, rare decays (BS, etc… )-- 4th generation-- SUSY -- Higgs triplets -- etc. etc.

Strong incentive to revisit and improve Z pole measurements and mW…


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?


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 MH ≈ 126 GeV?Any sign of new strong dynamics?

your Banker’s question: What precision is needed to see something interesting?


Some guidance from theorists

New physics affects the Higgs couplingsSUSY , 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

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

http://lcsim.org/papers/DBDPhysics.pdf


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.

if observed prod (gHi )2(gHf)2 extract couplings to anything you can see or produce from H if i=f as in WZ with H ZZ absoulte normalization

ConclusionsApproved 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, t 10-15%• t, 3-2

observation• gg and gg 5-11%

9November/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, t, 2-10%• gg and gg 2-5%• HHH >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: ATLASMC 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 gg 0-jet and VBFH tt VBF lep-lep and lep-hadH ZZ 4lH WW lnln 0-jet and VBFWH/ZH ggttH gg (ttH ) Direct top Y couplingH Second generation fermion

couplingHH bb gg Higgs Self-Couplings

10

ttH gg

November/14/2012 F.Cerutti - Higgs Factory

Very Robust channel

Good S/BStatistically limited


2030

HL-LHC will already be a Higgs factory, able to perform precise measurements on the relative values of the gg, gluon-gluon,tt, bb, , tt, 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 systematics2. assume theory systematics will reduce by 2 and exp errors as 1/sqrt(N) recall :LEP reduced by factor 10 several theory systematics

2021


b

t

Full HL-LHCZ

W

Ht

Rel

ativ

e


Higgs Factories Dreams


gg collider

Patrick Janot

+- Collider vs e+e- Collider ? A +- collider can do things that an e+e- collider cannot

dou Direct coupling to H expected to be larger by a factor m/me

l ,jh [peak = 70 pb at tree level]u Can it be built + beam energy spread dE/E be reduced to 3×10-5 ?

l 4D+6D Cooling needed!l For dE/E = 0.003% (dE ~ 3.6 MeV, H ~ 4 MeV)l no beamstrahlung, reduced bremsstrahlung

è Corresponding luminosity ~ 1031 cm-2s-1

Expect 2300 Higgs events in 100 pb-1/ yearu 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 ~ mHl Five-point scan, 50 + 100 + 200 + 100 + 50 pb-1

è Precision from H→bb and WW :

14 Nov 2012

HF2012 : Higgs beyond LHC (Experiments) 17

( ) ( )HeeH -+-+ 40000

(mH), TLEP

, W, …

, W, …

mH Peak H

0.1 MeV 0.6 pb 0.2 MeV

10-6 2.5% 5%

√s

(pb)

[16,17]


Neutrino Factory

MICE is one of the critical R&D experimentstowards 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 coolingrely 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 16-11-2012 Fermilab

Emittance exchange involves ionizationvarying 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 16-11-2012 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 ionizationvarying in space which cancels the dispersion of energies in the beam. This can be used to reduce the energyspread 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


The Higgs was barely missed at LEP2

LEP2: 26.7km circumference

4 IPs : L3, ALEPH, OPAL DELPHI

20MW of synchrotron radiation (scales as E4/R)

b* = 5cm luminosity lifetime ~ few hours

L = 1032 /cm2/s H=20%; 240fb 50 Higgses per exp per year!

able to do discovery, but not study!

What else?


ILC in a Nutshell

29.10.12

Damping RingsPolarised electron source

Polarised positronsource

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 TeVDrive Beam Generation Complex

Main Beam Generation Complex

140 s train length - 24 24 sub-pulses4.2 A - 2.4 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


The Higgs at a Linear e+e- Collider has been studied for many yearsCommunity 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 ECM , 1-2 1034/cm2/s at 500 GeV, one IP.

cost grows as A+BECM, both A and B are very large. ‘ready’. 10 years from approval to operation start 2025… if all goes very well

Latest reference:


Higgs production mechanism

Assuming that the Higgs is light, in an e+e– machine it is produced by the “higgstrahlung” process close to thresholdProduction xsection has a maximum at near threshold ~200 fb 1034/cm2/s 20’000 HZ events per year.

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= mH+11110 W. Lohmann et al LCWS/ILC2007

take 240 GeV.


e+

e-

Z*

Z

H

Z – tagging by missing mass

ILC

total rate gHZZ2

ZZZ final state gHZZ4/ H

measure total width H

empty recoil = invisible width‘funny recoil’ = exotic Higgs decayeasy 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 andcc

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?


b

t

Full HL-LHCZ

W

Ht

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 CERNJohn Osborne and Caroline Waiijer ESPP contr. 165

key parameters

LEP3, TLEP(e+e- -> ZH, e+e- → W+W-, e+e- → Z,[e+e-→ t )

LEP3 TLEPcircumference 26.7 km 80 kmmax beam energy 120 GeV 175 GeVmax no. of IPs 4 4 luminosity at 350 GeV c.m. - 0.7x1034 cm-2s-1 luminosity at 240 GeV c.m. 1034 cm-2s-1 5x1034 cm-2s-1 luminosity at 160 GeV c.m. 5x1034 cm-2s-1 2.5x1035 cm-2s-1 luminosity at 90 GeV c.m. 2x1035 cm-2s-1 1036 cm-2s-1

at the Z pole repeating LEP physics programme in a few minutes…

10-40 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 BfromR. 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

2012-11-15 HF2012 37

China Higgs Factory (CHF)

key parameters




10-40 times ILC lumi

at ZH thresh.

2-8 times ILC lumi

at ZH thresh.


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


gHZ gHb gHc gHg gHW gHt gHg gH H H,inv

key parameters




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.

42ICFA workshop on Higgs Factories, Fermilab 14-16- November 2012

beamstrahlung: reducing b* and increasing current leads to radiation of particlesin 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:


circular HFs – beamstrahlung

t>2 s at h=1.0% (4 IPs)t>37 s at h=1.5%

t>11 min at h=2.0% t>3h at h=2.5%

• simulation w 360M macroparticles • t varies exponentially w energy acceptance h• post-collision E tail → lifetime t

TLEP at 240 GeV:

M. Zanetti (MIT)

t>6 s at h=2.0% (4 IPs)t>37 s at h=2.5%t>3 min at h=3.0%

t>20 min at h=3.5%

TLEP at 350 GeV:


1. 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 90-370 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


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


all of this is for TLEP/VHE-LHC


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 measurementsand 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 gg, tt, , 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 EWRCmeasurements is strongly motivated. (Predicted mtop, mHiggs, now sensitive inclusively to EW-coupled new physics)


-- 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 resolutionson 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)

TLEP design study –preliminary structurefor discussion

Physics Experiments Accelerator

1. Theoretical implications and model building2. Precision measurements, simulations and monte-carlos3. Combination + complementarity with LHC and other machines ; global fits

1. H(126) properties2. Precision EW measurements at the Z peak and W threshold3. Top quark physics4. Experimental environment5. Detector design6. Online and offline computing

1. Optics, low beta, alignment and feedbacks2. Beam beam interaction3. Magnets and vacuum 4. RF system5. Injector system6. Integration w/(SHE)-LHC7. Interaction region8. Polarization &E-calib.9. Elements of costing

Steering group web site, mailing lists, speakers board, etc..

International Advisory board Institutional board


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 90-350 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 recommendedand you are very welcome to participate

https://espace.cern.ch/LEP3/

higgs factory workshop fermilab , 14-16 nov.2012

Documents

higgs mass

higgs boson couplings

discovered higgs

composite higgs

higgs couplingssusy

higgs triplets

higgs observables

higgs boson mass