Bottom-quark Fusion Processes at the LHC for …people.physics.tamu.edu/kamon/research/talk/2018/180723...Teruki Kamon Mitchell Institute for Fundamental Physics and Astronomy Texas

Teruki Kamon

Mitchell Institute for Fundamental Physics and Astronomy

Texas A&M University

26th International Conference on Supersymmetry and Unification of

Fundamental Interactions (SUSY2018)

23rd ‐ 27th July, Barcelona, Spain

1July 26, 2018 B-Fusion Zprime

[Credits]

Images of Baryon Acoustic Bscillations with Cosmic Microwave Background

by E.M. Huff, the SDSS-III team, and the South Pole Telescope team. Graphic

by Zosia Rostomian (Lawrence Berkeley National Laboratory)

Image of Neutrino Astrophysics, taken from https://astro.desy.de/

Image of the LHC by CERN Photo

Image of Bullet Cluster by NASA/ Chandra X-ray Center

Bottom-quark Fusion Processes

at the LHC for Probing 𝒁′ Models and B-meson Decay Anomalies

© My Daughter

https://astro.desy.de/

Prologue

4 sigma tension in flavor physics?

SM

BSM

Nature of flavor physics?

𝑹𝑲(∗)

𝑹𝑫(∗)

Phenomenology study:

@ Corpus Christi, Texas, USA

MADGRAPH5 v.2.5.4

PYTHIA 8.2

DELPHES 3.4

arXiv:1707.07016, Phys. Rev. D 97 (2018) 075035

Teruki Kamon 2B-fusion Zprime

Deviation at 2.4𝜎 - 2.6𝜎 from the SM Compatible with other anomalies observed in

𝑏 → 𝑠𝜇𝜇 transition~4𝜎 tension with SM

Puzzle with Anomalies in B Decays

New contribution?


1


Physics Model for B AnomaliesNew physics contribution can be expressed as:

The best fit values for C9 is:

Z’ in a minimal phenomenological setting is:

Selective U(1) fermion charges to evade current LH and LEP constraints.

Coupling to muons in leptonic sector and b-s in fermionic sector.

Adding muon neutrino and top quark couplings to preserve SU(2).

Considering tau decays

𝐿 ⊃ 𝑍′𝜇 [𝑔𝜇𝑉 ҧ𝜇𝛾𝛼𝜇 + 𝑔𝜇

𝑉 ҧ𝜈𝜇𝛾𝛼𝑃𝐿 𝜈𝜇 + 𝑔𝑏

𝑞= 𝑡,𝑏

ത𝑞𝛾𝛼𝑃𝐿 𝑞 + (𝑔𝑏 𝛿𝑏𝑠𝐿 ҧ𝑠𝛾𝛼𝑃𝐿 𝑏 + ℎ. 𝑐. ) ]

2

3

4

Teruki Kamon 5

𝒁′ Production via B-Fusion at LHC

B-fusion Zprime

Bottom Fermion Fusion (BFF)

Bottom-strange quark fusion

ҧ𝑠

𝑔𝑏𝛿𝑏𝑠



𝑞= 𝑡,𝑏


3


ҧ𝑠

𝑔𝑏𝛿𝑏𝑠

𝜎 𝑍′ to be consistent with anomalies in B meson decays depends on 𝑔𝑏 for larger 𝑔𝑏 or 𝑔𝑏𝛿𝑏𝑠 for smaller 𝑔𝑏:

Production Cross Section at LHC

Larger 𝒈𝒃 (bb fusion)2b+2m+jets

Smaller 𝒈𝒃(bs fusion)1b+2m+jets

𝑔𝑏𝛿𝑏𝑠𝑔𝜇𝑉 Τ100 GeV 𝑀𝑍′

2

≈ 1.3 × 10−5

𝑀𝑍′ = 350 GeV 𝑔𝜇 = 0.13

4

~15 fb at 500 GeV

Fig. 3

Physics Letters B 761 (2016) 372–392

𝒁′ → 𝝁𝝁 at ATLAS and CMS

[Constraints from current inclusive di-muon resonance searches] The ATLAS limit for 500-GeV 𝑍′ is ~15 fb from Fig. 3. The leptonic production for the

SM 𝑍 is 1.981 nb from the ATLAS paper (cf. 1.89 nb at DYNNLO). Thus the ATLAS limiton the cross section ratio R = 15 fb / 1.9 nb = 7.9x10^-6.

The corresponding CMS limit on R is 1.4x10^-6 from Fig. 3b (CMS-EXO-16-047, CERN-EP-2018-027), which is stringent compared to the ATLAS result.

Fig. 3b

𝑅 = 1.4 × 10−6 at 500 GeV

JHEP 06 (2018) 120

SM background becomes dominant for MZ’ < 500 GeV. Di-jet, 𝑡 ҧ𝑡 resonance searches produce weaker limits. Below 500 GeV, di-muon resonance + ≥1 b tagged jet.



Final States at LHC Two main backgrounds: (i) SM DY 𝛾∗/Z + jets, (ii) top quark production. Use ISR jets to reduce the SM background


Final States at LHC Two main backgrounds: (i) SM DY 𝛾∗/Z + jets, (ii) top quark production. Use ISR jets to reduce the SM background

2 b-s fusion both b and s from gluon

splitting


Final States at LHC

OS di-muon resonance + ≥ 1 b tagged jet (at least 2jets)

MLM matching with xqcut = 30 and qcut = 60 for smooth DJR and being insensitive to physical observables (e.g., cross section, kinematical distributions)

Two main backgrounds: (i) SM DY 𝛾∗/Z + jets, (ii) top quark production. Use ISR jets to reduce the SM background

2 b-s fusion both b and s from gluon

splitting

All jet multiplicities must be generated together to resolve ambiguities between sea bottom-quarks from the PDFs and bottom-quark pairs from gluino splitting:

pp > zp zp, zp > mu+ mu- @0 pp > zp j, zp > mu+ mu- @1 pp > zp j j, zp > mu+ mu- @2

with p = p b b~ and j = j b b~

Search for BFF 𝒁′ at LHC

𝑀𝑏𝜇 or 𝑀𝜇𝑗 > 170 GeV (top mass bound)

ൗ𝐸𝑇𝑚𝑖𝑠𝑠

𝑀𝜇𝜇 < 0.2𝐻𝑇 − 𝐿𝑇 < 0 (hadronic vs. leptonic activity)

[Preselection] OS di-muon + ≥ 1 b tagged jet (at least 2jets)


MADGRAPH5 v.2.5.4

PYTHIA 8.2

DELPHES 3.4 (CMS

card)


“Unboosted” 𝒎𝐓𝟐 - I am Number Four

We didn’t use the 4th requirement (unboosted 𝑚T2), which provides a good discrimination, but does not improve its sensitivity.

unboosted 𝑚T2𝑚T2

Teruki Kamon 13

Limit Extraction

B-fusion Zprime

• 𝑔𝜇 = 1 for calculating Z’ decay width • The significance increases for smaller 𝑔𝜇 .


Allowed regions (yellow/green) in 𝛿𝑏𝑠-𝑔𝑏

Current & Future Constraints

Neutrino trident constraints

𝑀𝑍′ = 350 GeV𝑀𝑍′ = 200 GeV 𝑀𝑍′ = 500 GeV

𝑔𝑏

𝛿𝑏𝑠

CMS Inclusive search

BFF Z’ search [Phys. Rev. D 97 (2018) 075035]

1 s.d. band for B anomalies

2 s.d. band for B anomalies

Teruki Kamon 15

BFF 𝒁′ Summary

B-fusion Zprime

Anomalies in B meson decays - oneof hot topics

Can be explained with models of Z’coupling to b, s and muon.

Prospects for a dedicated search for b-associated Z‘production by ATLAS and CMS [Phys. Rev. D 97 (2018) 075035]:

1) Z’ couples to third generation SM particles should be studied withdi-muon + ≥ 1 b events via b-fusion processes and flavor violating b-s-Z’ process. The flavor violating b-s-Z’ coupling introduces a minimumproduction cross-section.

2) The limits on 𝜎 ∙ 𝐵 in the existing inclusive di-muon searches can beapplied to these model parameter space. The reach can be improvedby utilizing di-muon + ≥ 1 b for 350 GeV or lighter Z’.

3) 𝑝𝑝 → 𝑍′ → 𝑏𝑏 or 𝑏𝑠 and 𝑝𝑝 → 𝑍′ → 𝑡𝑡 for further understanding ofsuch models.

© My Daughter

16

Backups

Operators and New Physics

[Altmannshofer, DPF’17 talk]

Dipole Operators do not break lepton universality. Scalar operators are strongly constrained by 𝐵𝑠 → ℓ

+ℓ− [Alonso, Grinstein, Martin Camalich,’14]

Semileptonic operators are needed. Right handed current produce anti-correlation between Rk and Rk* [Hiller,

Schmaltz,’14]

17



𝑞=𝑡,𝑏


𝐿 ⊃ 𝑍′𝜇 [𝑔𝜇𝑉 ҧ𝜇𝛾𝛼𝜇 + (𝑔𝑏 𝛿𝑏𝑠

𝐿 ҧ𝑠𝛾𝛼𝑃𝐿 𝑏 + ℎ. 𝑐. ) ]

𝑉𝑡𝑏𝑉𝑡𝑠∗

𝑒2

16𝜋2𝐶9 = 𝑔𝑏 𝛿𝑏𝑠

𝐿 𝑔𝜇𝑉

𝑣2

2𝑀𝑍′2

Minimal Lagrangian:

Many models can generate this Lagrangian, e.g., using Vector-like quarks (Q):

Avoid first generation coupling to Z’: strong constraint O(few TeV)

e.g., Altmannshofer, Yavin, 2015,

Many more references (see , arXiv:1707.07016 for a full list)

Simple Models

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Production

Z’ is suppressed by a factor of 1/M(Z’)2 in addition to the bottom PDF

The radiative suppression is solved with g bb, but adding a gluon splitting fraction in addition to the bottom PDF

Bottom quark fusion via gluon splitting to bb -- Z’ production associated with b jets

19

20

Z’ Decay Widths



𝑞=𝑡,𝑏


21

Some Constraints

DBS =0.07 ± 0.09

Weak constraints from neutrino trident production and contributions to muon g-2

Allanach, Queiroz, Strumia, Sun, 2016

Q&A for BFF Z’ Models1) We assume same couplings to bb and tt (g_b).

In the simplified model, we assume the 𝑍′ couples uniformly to top and bottombecause of SU(2) invariance. The Lagrangian is written with (𝜈𝜇, 𝜇) and (𝑡, 𝑏), and 𝛿𝑏𝑠,

𝑔𝜇 and 𝑔𝑏 to explain B-meson decay anomalies, We can test via 𝑍′(→ 𝜇𝜇) + bb and

𝑍′(→ 𝑏𝑏) + bb. Since we don’t know a true nature of 𝑍′ yet, using a simple frameworkis good enough. Once we see any excess, we can move to more detailed models.

2) We obtain a better result than current analysis (for low mass Z') byhaving dedicated search for Z'-->mumu + b’s.

The acceptance of requiring extra jets and at least one b-tag among them is of courseworse than just requiring muons. But the losses in acceptance for the signal areoutdone by the background suppression, most notably on the DY part (totalacceptance for offshell DY events is ~10^-4 while it is ~10^-3 for 𝑡 ҧ𝑡 evets) , whenyou look for smaller 𝑍′ masses closer to the 𝑍 peak. Our dominant backgroundbecomes ttbar beyond around 150 GeV in our dimuon mass spectrum, as is mosteasily visible in Figure 3. So for higher masses, the inclusive analysis will always outdothe BFF analysis. For lower masses though, S/sqrt(S+B) looks better in this Delphesstudy.

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Documents

Bottom-quark Fusion Processes at the LHC for …people.physics.tamu.edu/kamon/research/talk/2018/180723...Teruki Kamon Mitchell Institute for Fundamental Physics and Astronomy Texas