1

Tim BarklowSLACMass Higgs Chapter MeetingFeb 11, 2020

Photon Collider H(125) Factory

2 2

Let's look at H(125) production through s-channel annihilation of the colliding beam particles ,

For SM Higgs, M 125 GeV4.03 MeV9.33 KeV

,

0.89 KeV

0.02 eV

A measure

m

H

tot

e e

e e

γγ

µ µ

µ µ γγ

+ −

+ −

+ − + −

=

Γ =

Γ =

Γ =

Γ =

ent of ( (125)) is mentioned in FCC-ee Higgs studies as a means to access the electron Yukawa coupling, but s-channel Higgs production certainly can't be used as a Higgs factory.

Muon collid

e e He e

σ + −

+ −

→

er Higgs factories have been discussed that operate with / 0.01% in order to match 4.03 MeV. However, there are a lot of technical challenges (muon beam emittance, neutrino radiation

beam beam

tot

E E∆ <

Γ = hazard,background from electrons produced in beam muon decay, ...).

The SM partial width is 10 times the partial width. Is there any way to operate a collider with a very small center of

γγ µ µ γγγγ

+ −

mass energy spread to take advantage of the relatively large partial width? With a total width of 4 MeV, the smaller you make the center of mass energy spread the greater your Higgs production

γγγγ rate

3 3

Photon Collider Basics

Photons from a high powered laser are scattered off the high energy beam electrons of a linear collider between the final quadrupole and the interaction point. The compton scattered photons acquire the momenta of the high energy electrons and collide at the i.p. with the compton scattered photons from the opposing beam. The luminosity will be given by the geometric e eγγ + − luminosity times the compton conversion efficiency squared.

( )0

02 20

2

0

4 1

11 /

( 1) center of mass energy squared of electron and laser photon laser photon energy

compton scattered (high energy) photon en

e emm e

e e

e

E mxx E xx Em

m x

ω ωω ω θ

θ θ

ωω

−

−

−

= = = = +++

+ =

=

= ergy angle of compton scattered (high energy) photon w.r.t. electronθ =

4 4

In the following slides I calculate the Higgs production rate while varying , , and , where

= mean helicity of laser beam | | 11 = mean helicity of electron beam | |2

The thresholds

c e

c c

e e

x P

P P

λ

λ λ

≤

≤

laser

for two important physics processes are crossed as is varied

At 4.82 opens up which depletes the high energy photon beam; this effect is included in the Higgs cross section calculati

x

x e eγγ + −= →

laser

on and is given by the variable

At 8 opens up. This process smears the electron energy and hence smears the high energy photon spectrum. The effects of this process are not inc

x e e e e

κ

γ− + − −= →

1

l

2

ase

luded.

The luminosity spectrum is plotted, along with where

mean helicity of the high ene

Note: All Higgs cross sec

rgy photon beam i,

tions must be multip

i

l

=1,2

ied by the

| | 1i i

e γ

γγ ξ ξ

ξ ξ

−

⟨ ⟩

= ≤

r

Strong field nonlinear effects are not i

conversion

ncluded unle

probabi

ss othe

li

rw

ty squared

ise noted

5 5

γγ − −= /e e

z E E

γγ

− −

1

e e

dLL dz

ξ ξ< >1 2

γγ − −= /e e

z E E

γγ

γγ

πσ γγ ξ ξ

πξ ξ δ

Γ Γ→ = +

− + Γ

Γ≈ + −

1 22 2 2 2

2

1 23

8( ) (1 )

( )4

(1 ) ( )

tot

H tot H

H HH

Hs M M

z z zM

γγ

κ

λ

κ γ γ

σ γγ

− −

− −

−

= =

= = −

−

→ =∫

4.82 158 GeV =1

pol( ) 90% 2 0.9

( = 1 prob that annihilates with laser )

1 ( ) 247 fb

e e

c e

e e

x E

e P

dLdz H

L dz

Nominal configuration

6 6

γγ−1CLICHE Study x=4.1 200 fb luminosityFull Compton collision simulation with CAIN. Fast MC Detector Simulation

arXiv:hep-ex/0111056

7 7

8 8

ILC

ILC

9 9

γγ − −= /e e

z E E

γγ

− −

1

e e

dLL dz

ξ ξ< >1 2

γγ − −= /e e

z E E

γγ

κ

λ

σ γγ

− −

− −

−

= =

= = −

→ =∫

6.00 150 GeV =0.73

pol( ) 90% 2 0.9

1 ( ) 130 fb

e e

c e

e e

x E

e P

dLdz H

L dz

Now let's start increasing x (the energy of the Compton photon)

10 10

γγ − −= /e e

z E E

γγ

− −

1

e e

dLL dz

ξ ξ< >1 2

γγ − −= /e e

z E E

γγ

κ

λ

σ γγ

− −

− −

−

= =

= = −

→ =∫

8.00 146.5 GeV =0.48

pol( ) 90% 2 0.9

1 ( ) 78 fb

e e

c e

e e

x E

e P

dLdz H

L dz

11 11

γγ − −= /e e

z E E

γγ

− −

1

e e

dLL dz

ξ ξ< >1 2

γγ − −= /e e

z E E

γγ

κ

λ

σ γγ

− −

− −

−

= =

= = −

→ =∫

20.00 134.8 GeV =0.25

pol( ) 90% 2 0.9

1 ( ) 40 fb

e e

c e

e e

x E

e P

dLdz H

L dz

12 12

γγ − −= /e e

z E E

γγ

− −

1

e e

dLL dz

ξ ξ< >1 2

γγ − −= /e e

z E E

γγ

κ

λ

σ γγ

− −

− −

−

= =

= = −

→ =∫

40.00 130.3 GeV =0.19

pol( ) 90% 2 0.9

1 ( ) 42 fb

e e

c e

e e

x E

e P

dLdz H

L dz

13 13

γγ − −= /e e

z E E

γγ

− −

1

e e

dLL dz

ξ ξ< >1 2

γγ − −= /e e

z E E

γγ

κ

λ

σ γγ

− −

− −

−

= =

= = −

→ =∫

1000. 126.2 GeV =0.11

pol( ) 90% 2 0.9

1 ( ) 257 fb

e e

c e

e e

x E

e P

dLdz H

L dz

14 14

γγ − −= /e e

z E E

γγ

− −

1

e e

dLL dz

ξ ξ< >1 2

γγ − −= /e e

z E E

γγ

κ

λ

σ γγ

− −

− −

−

= =

= = +

→ =∫

1000. 126.6 GeV =0.44

pol( ) 90% 2 0.9

1 ( ) 311 fb

e e

c e

e e

x E

e P

dLdz H

L dz

15 15

γγ − −= /e e

z E E

γγ

− −

1

e e

dLL dz

ξ ξ< >1 2

γγ − −= /e e

z E E

γγ

κ

λ

σ γγ

− −

− −

−

= =

= = −

→ =∫

4000. 126 GeV =0.12

pol( ) 90% 2 0.9

1 ( ) 1099 fb

e e

c e

e e

x E

e P

dLdz H

L dz

16 16

γγ − −= /e e

z E E

γγ

− −

1

e e

dLL dz

ξ ξ< >1 2

γγ − −= /e e

z E E

γγ

κ

λ

σ γγ

− −

− −

−

= =

= = +

→ =∫

4000. 126.2 GeV =0.53

pol( ) 90% 2 0.9

1 ( ) 1188 fb

e e

c e

e e

x E

e P

dLdz H

L dz

17 17

γγ − −= /e e

z E E

γγ

− −

1

e e

dLL dz

ξ ξ< >1 2

γγ − −= /e e

z E E

γγ

κ

λ

σ γγ

− −

− −

−

= =

= = −

→ =∫

15870. 126 GeV =0.15

pol( ) 90% 2 0.9

1 ( ) 5614 fb

e e

c e

e e

x E

e P

dLdz H

L dz

18 18

γγ − −= /e e

z E E

γγ

− −

1

e e

dLL dz

ξ ξ< >1 2

γγ − −= /e e

z E E

γγ

κ

λ

σ γγ

− −

− −

−

= =

= = +

→ =∫

15870. 126 GeV =0.64

pol( ) 90% 2 0.9

1 ( ) 4792 fb

e e

c e

e e

x E

e P

dLdz H

L dz

λ

λ

= +

∆ ≈

= −

2 0.9 is a better match to / 0.1% than 2 0.9 for this large x value.

c e

beam beam

c e

PE E

P

19 19

γγ

− −

1

e e

dLL dz

− − (final state)/ (initial)e e

E E

κ

λ

− −

−

= =

= = +

15870. 126 GeV =0.64

pol( ) 90% 2 0.9e e

c e

x E

e P

γγ − −= /e e

z E E

γ

γ

σ γ γ

γ

σ γ

−

−

−

−

−

+

− −

−

+ −

−

→ = × →=

→=

V

Lab electron energy spectrum following single Bethe-Heitlerinteraction for (initial)=63 GeV, E

Problem: ( ) 20 ( ) for =63 Ge

e

V, E 1

15

5 ke

k V

e

e

e e eE

e e e

e

e e eE

0.955 0.97 0.985 1.00

γ− − − +→ e e e e

20 20

γγ

γγ + −→

Existing compton collision parameters are optimal for a Higgs factory unless you go to very large values of x where the lumi spectrum is sharply peaked and is suppressed via polarization. e e

λ = +

Assuming electron energy spread is dominated by accelerator energy spread, and disregarding the extreme laser technical challenges the optimal x value was x=16000 with 2 0.9. The Higgs productionc eP

γγ rate in this configuration

was 20 times the nominal collider rate.

Unfortunately, it appears that at large x values the electron energy spread is not dominated by the accelerator but rather by the γ− − − +→laser Bethe-Heitler process . This needs to be investigated. CAIN documentation indicates that it can simulatethis process, but this has to be verified.

Nonlinear strong field effects h

e e e e

γγ γ γ+ − − −→ →laser laser

ave to be incorporated into this study. CAIN can simulatenonlinear and .e e e e

21 21

γγ

−

− −

≈

Using an x-ray laser at the Compton collision point and the gamma/

polarizations shown on the previous slides, a =125 GeV collideroperating in mode could produce 1M Higgs bosons in a 5 yea

e

s e e

γγ

γγ

γ−

≈r

period with a center-of-mass energy spread of 200 MeV.

We need to use the CAIN MC program to determine how the propertiesare affected by non-linear QED effects, the Bethe-Heiler process e

γγ

− − +→laser ,electron energy spread, and X-ray laser energy spread.

These affects will increase the center of mass energy spread and reduce the Higgs production rate. The question is by how much.

e e e

22 22

γγσ

With a more realistic simulation of the beam conditions then we would use afast MC simulation of SiD to estimate XBR for various Higgs final states,perhaps with different sets of initial state ga

γγ

mmma polarizations.How much, if anything, a gamma-gamma center-of-mass energy scan can tell us about the total Higgs width will depend on the center-of-mass energy spread predicted by the full CAIN simulation.

We need to then address the question of the physics reach under various scenarios (gamma-gamma colider with or without a 250 GeV e+e- collider,with or without FCC-hh, etc.)