1. Higgs in Collins-Soper land
Measurements on the Higgs spin and CP
Nikhef Atlas Outing 2014
Koen Oussoren

2. Koen Oussoren - Atlas Outing 2014
Content
Why spin & CP?
Current spin analysis in HWW channel
Collins-Soper Frame
Variables of interest
Reco Higgs
Prospects and Challenges
Conclusion
Koen Oussoren - Atlas Outing 2014

3. Koen Oussoren - Atlas Outing 2014
Why spin and CP?
SM is boring
Something new would spice up things a bit
Different models predict Higgs to have different spin/CP, so not scalar-like
Testing our understanding of the physics
Spin/CP studies mainly involve shape analysis and are complementary to rate and coupling analysis
Koen Oussoren - Atlas Outing 2014

4. Koen Oussoren - Atlas Outing 2014
HWW analysis
Higgs decay to WW
Dileptonic W decay
Events to look for have 2 leptons and quite a bit of missing transverse energy
Spin analysis revolved mainly around lepton kinematics
Outcome: What we see is pretty much SM-like
CP-mixing analysis
Mixture between SM-like and pseudo-scalar Higgs
Setting limits on mixing angle α
BDT analysis
My current contribution?
General method for finding Fourier components of lepton angles and momenta in a specifically chosen Higgs rest frame
Koen Oussoren - Atlas Outing 2014

5. Koen Oussoren - Atlas Outing 2014
Collins-Soper frame
First used by Collins-Soper to modify the Drell-Yan model to account for transverse momentum (1977)
Particles B and A are gluons (quarks) that fuse into a Higgs.
Z-axis is the bisection of Pa and –Pb
X-axis is “away”-vector of Pa+Pb and also direction of the Higgs in lab frame
Koen Oussoren - Atlas Outing 2014

6. Koen Oussoren - Atlas Outing 2014
Angles
Angles θ and ϕ are well defined in this frame
Together with the momentum of the leptons all the information on Higgs spin/CP is available
Any preference for the angles and the momentum will not be washed out in the CS-frame
Interesting for studies on C, P and T violation x φ θ z
z lab y
Koen Oussoren - Atlas Outing 2014

7. Koen Oussoren - Atlas Outing 2014
What to expect?
Δφll and Δθll
Small for spin-0 Higgs, large for spin-2 resonances
ΔPll and SumPll
Sum and difference of momentum magnitude l+ and l-
Information on the energy of the on and off-shell W
Koen Oussoren - Atlas Outing 2014

8. Jp = 0+
0+ scalar W decay
Polar Angle theta 0- 1-

9. Jp = 0+
0+ scalar W decay
SP and DP 0- 1-

10. Koen Oussoren - Atlas Outing 20140+
Jp = 0+ 0- 0-
Koen Oussoren - Atlas Outing 2014

11. Koen Oussoren - Atlas Outing 2014
Strategy
Fourier decomposition
For ΔPll and SumPll this is relatively simple
1D problem and symmetric components only
θ and φ are a bit more complicated
Work in progress
Koen Oussoren - Atlas Outing 2014

12. 0+
SumP p0: ,sig: 424
SumP p1: ,sig: 1362
SumP p2: ,sig: 368
SumP p3: ,sig: 166
SumP p4: ,sig:
SumP p5: ,sig:
SumP p6: ,sig:
SumP p7: ,sig:
SumP p8: ,sig:
SumP p9: ,sig:
NAH! 0-
SumP p0: ,sig: 424
SumP p1: ,sig: 1622
SumP p2: ,sig: 433
SumP p3: ,sig: 195
SumP p4: ,sig: 108
SumP p5: ,sig:
SumP p6: ,sig:
SumP p7: ,sig:
SumP p8: ,sig:
SumP p9: ,sig:

13. 0+
DeltaP p0: ,sig: 424
DeltaP p1: ,sig: 427
DeltaP p2: ,sig: 131
DeltaP p3: ,sig: 119
DeltaP p4: ,sig: 30
DeltaP p5: ,sig:
DeltaP p6: ,sig:
DeltaP p7: ,sig:
DeltaP p8: ,sig:
DeltaP p9: ,sig: 0-
DeltaP p0: ,sig: 424
DeltaP p1: ,sig: 280
DeltaP p2: ,sig: 32
DeltaP p3: ,sig: 97
DeltaP p4: ,sig: 47
DeltaP p5: ,sig: 9
DeltaP p6: ,sig: 9
DeltaP p7: ,sig: 6
DeltaP p8: ,sig: 1
DeltaP p9: ,sig: 2

14. Koen Oussoren - Atlas Outing 2014
Reco Higgs
Nice! But how about the neutrinos?
See Rosemarie’s talk
Reco code
Reconstruct z-component of di-neutrino system
Now able to boost to CS-frame
Let’s see what happens with ΔPll
Koen Oussoren - Atlas Outing 2014

15. 0+ 0+
RECO 0- 0-
RECO

16. Koen Oussoren - Atlas Outing 2014
Prospects
CP-Mixings analysis
See how the most significant parameters change with cos(α)
Plots below show cos(α) = 0, 0.25, 0.5, 0.75, 1 (SM Higgs)
Higher dimensional operators (HDO)
See how HDOs influence the parameter values
Koen Oussoren - Atlas Outing 2014

17. Koen Oussoren - Atlas Outing 2014

18. Challenges 0+ 0+
CUTS 0- 0-
CUTS

19. Koen Oussoren - Atlas Outing 2014
Conclusion
CS-frame
Interesting for studies on spin/CP
Mixing scalar/pseudo-scalar
Future
Detector level, cuts and background
Parameter scan for mixing and HDOs
Koen Oussoren - Atlas Outing 2014

20. Koen Oussoren - Atlas Outing 2014
Back up
Koen Oussoren - Atlas Outing 2014