M ULTIBOSON SIGNALS IN THE UN2HDM
João Seabra
Instituto de Física Teórica UAM-CSIC, Campus de Cantoblanco, Madrid
XIII CPAN Days
21st of March 2022
Ongoing work done in collaboration with: Juan A. Aguilar-Saavedra and Filipe R. Joaquim CFTP, Instituto Superior Técnico, Lisboa
UN2HDM
• It extends the Standard Model (SM) gauge symmetry with an additional U(1) group:
UN2HDM
• It extends the Standard Model (SM) gauge symmetry with an additional U(1) group:
New massive gauge boson
UN2HDM
• It extends the Standard Model (SM) gauge symmetry with an additional U(1) group:
New massive gauge boson
• The neutral and colour-singlet boson must be leptophobic;
UN2HDM
• It extends the Standard Model (SM) gauge symmetry with an additional U(1) group:
New massive gauge boson
• The neutral and colour-singlet boson must be leptophobic;
• Its scalar sector is formed by two complex scalar doublets ( , ) and one complex scalar singlet ( );
UN2HDM
• It extends the Standard Model (SM) gauge symmetry with an additional U(1) group:
New massive gauge boson
• The neutral and colour-singlet boson must be leptophobic;
• As in a Type I 2HDM, flavour-changing neutral currents (FCNCs) are avoided by preventing Yukawa couplings between fermions and one Higgs doublet,
• Its scalar sector is formed by two complex scalar doublets ( , ) and one complex scalar singlet ( );
UN2HDM
• It extends the Standard Model (SM) gauge symmetry with an additional U(1) group:
New massive gauge boson
• The neutral and colour-singlet boson must be leptophobic;
• As in a Type I 2HDM, flavour-changing neutral currents (FCNCs) are avoided by preventing Yukawa couplings between fermions and one Higgs doublet,
• Its scalar sector is formed by two complex scalar doublets ( , ) and one complex scalar singlet ( );
UN2HDM
• It extends the Standard Model (SM) gauge symmetry with an additional U(1) group:
New massive gauge boson
• The neutral and colour-singlet boson must be leptophobic;
• As in a Type I 2HDM, flavour-changing neutral currents (FCNCs) are avoided by preventing Yukawa couplings between fermions and one Higgs doublet,
• Its scalar sector is formed by two complex scalar doublets ( , ) and one complex scalar singlet ( );
Gauge inv.
UN2HDM
• It extends the Standard Model (SM) gauge symmetry with an additional U(1) group:
New massive gauge boson
• The neutral and colour-singlet boson must be leptophobic;
• As in a Type I 2HDM, flavour-changing neutral currents (FCNCs) are avoided by preventing Yukawa couplings between fermions and one Higgs doublet,
• Its scalar sector is formed by two complex scalar doublets ( , ) and one complex scalar singlet ( );
Gauge inv. Gauge inv.
UN2HDM
• It extends the Standard Model (SM) gauge symmetry with an additional U(1) group:
New massive gauge boson
• The neutral and colour-singlet boson must be leptophobic;
• As in a Type I 2HDM, flavour-changing neutral currents (FCNCs) are avoided by preventing Yukawa couplings between fermions and one Higgs doublet,
• Its scalar sector is formed by two complex scalar doublets ( , ) and one complex scalar singlet ( );
Gauge inv.
• Extra matter must be introduced to cancel anomalies associated with U(1)’.
Gauge inv.
E XTRA MATTER AND U(1)’ HYPERCHARGES
SM fermions:
E XTRA MATTER AND U(1)’ HYPERCHARGES
Assuming extra matter to be vector-like, we can:
SM fermions:
E XTRA MATTER AND U(1)’ HYPERCHARGES
Assuming extra matter to be vector-like, we can:
• Add a set of vector-like quarks...
Heavy fermion mass terms and a valid scalar mass spectrum can be generated
by considering .
SM fermions:
Assuming extra matter to be vector-like, we can:
• ... or a set of vector-like leptons.
Heavy fermion mass terms and a valid scalar mass spectrum can be generated
by considering .
SM fermions:
E XTRA MATTER AND U(1)’ HYPERCHARGES
S CALAR POTENTIAL
S CALAR POTENTIAL
Scalar fields
Vacuum expectation values (VEVs)
S CALAR POTENTIAL
Scalar fields
Vacuum expectation values (VEVs)
Rephasing
S CALAR POTENTIAL
Scalar fields
Vacuum expectation values (VEVs)
Rephasing
if
S CALAR POTENTIAL
Scalar fields
Vacuum expectation values (VEVs)
All VEVs can be assumed as real without loss of generality.
Rephasing
if
S CALAR POTENTIAL
Note:
Henceforth, the VEVs and are represented in terms of
Minimum conditions
The parameters and can be written in terms of the five scalar masses and the three mixing angles of CP-even scalars.
S CALAR POTENTIAL – P ARAMETER RECONSTRUCTION
• From the nonzero eigenvalues of the mass matrices of charged scalars and pseudoscalars, we get:
S CALAR POTENTIAL – P ARAMETER RECONSTRUCTION
• From the nonzero eigenvalues of the mass matrices of charged scalars and pseudoscalars, we get:
• The remaining six parameters are read from the mass matrix of CP-even scalars:
S CALAR POTENTIAL – P ARAMETER RECONSTRUCTION
• From the nonzero eigenvalues of the mass matrices of charged scalars and pseudoscalars, we get:
• The remaining six parameters are read from the mass matrix of CP-even scalars:
There are no free parameters in the scalar potential of the UN2HDM.
G AUGE BOSON MASS LAGRANGIAN
G AUGE BOSON MASS LAGRANGIAN
G AUGE BOSON MASS LAGRANGIAN
From the diagonalisation of the mass matrix of neutral gauge bosons,
G AUGE BOSON MASS LAGRANGIAN
From the diagonalisation of the mass matrix of neutral gauge bosons,
Weak-mixing angle Z-Z’ mixing angle
G AUGE BOSON MASS LAGRANGIAN
From the diagonalisation of the mass matrix of neutral gauge bosons,
Weak-mixing angle Z-Z’ mixing angle
An expression for the VEV of the singlet can be found from the formulas above:
G AUGE BOSON MASS SPECTRUM
In the limit where the Z-Z’ mixing angle is very small:
G AUGE BOSON MASS SPECTRUM
In the limit where the Z-Z’ mixing angle is very small:
The approximations above are valid in the limit where
An approximation for the Z-Z’ mixing angle can be found from the formulas for the masses of Z and Z’:
Q UESTION ...
What makes the UN2HDM interesting?
Q UESTION ...
• Predicted in many theoretical frameworks beyond the SM, cascade decays originated by yet unseen particles might lead to distinctive experimental signatures at the Large Hadron Collider (LHC);
What makes the UN2HDM interesting?
e.g. J. A. Aguilar-Saavedra, F. R. Joaquim; JHEP 01 (2016) 183 K. S. Agasheet al.; JHEP 05 (2017) 78
Q UESTION ...
• Models with an extra U(1) symmetry have been shown to be an example of such a framework.
• Predicted in many theoretical frameworks beyond the SM, cascade decays originated by yet unseen particles might lead to distinctive experimental signatures at the Large Hadron Collider (LHC);
What makes the UN2HDM interesting?
Example: Minimal stealth boson model (MSBM)
e.g. J. A. Aguilar-Saavedra, F. R. Joaquim; JHEP 01 (2016) 183 K. S. Agasheet al.; JHEP 05 (2017) 78
Q UESTION ...
• Models with an extra U(1) symmetry have been shown to be an example of such a framework.
• Predicted in many theoretical frameworks beyond the SM, cascade decays originated by yet unseen particles might lead to distinctive experimental signatures at the Large Hadron Collider (LHC);
What makes the UN2HDM interesting?
Example: Minimal stealth boson model (MSBM)
o Its scalar sector is only extended with two scalars that are SM singlets but charged under the extra U(1) group;
e.g. J. A. Aguilar-Saavedra, F. R. Joaquim; JHEP 01 (2016) 183 K. S. Agasheet al.; JHEP 05 (2017) 78
Q UESTION ...
• Models with an extra U(1) symmetry have been shown to be an example of such a framework.
• Predicted in many theoretical frameworks beyond the SM, cascade decays originated by yet unseen particles might lead to distinctive experimental signatures at the Large Hadron Collider (LHC);
What makes the UN2HDM interesting?
Example: Minimal stealth boson model (MSBM)
o Its scalar sector is only extended with two scalars that are SM singlets but charged under the extra U(1) group;
o After being produced by the decay of a heavy Z’ boson, scalars may decay hadronically, producing a four-pronged jet;
e.g. J. A. Aguilar-Saavedra, F. R. Joaquim; JHEP 01 (2016) 183 K. S. Agasheet al.; JHEP 05 (2017) 78
J. A. Aguilar-Saavedra, F. R. Joaquim; JHEP 10 (2019) 237 J. A. Aguilar-Saavedra, F. R. Joaquim; Eur.Phys.J.C 80 (2020) 5, 403
Q UESTION ...
• Models with an extra U(1) symmetry have been shown to be an example of such a framework.
• Predicted in many theoretical frameworks beyond the SM, cascade decays originated by yet unseen particles might lead to distinctive experimental signatures at the Large Hadron Collider (LHC);
What makes the UN2HDM interesting?
Example: Minimal stealth boson model (MSBM)
o Its scalar sector is only extended with two scalars that are SM singlets but charged under the extra U(1) group;
o After being produced by the decay of a heavy Z’ boson, scalars may decay hadronically, producing a four-pronged jet;
e.g. J. A. Aguilar-Saavedra, F. R. Joaquim; JHEP 01 (2016) 183 K. S. Agasheet al.; JHEP 05 (2017) 78
J. A. Aguilar-Saavedra, F. R. Joaquim; JHEP 10 (2019) 237 J. A. Aguilar-Saavedra, F. R. Joaquim; Eur.Phys.J.C 80 (2020) 5, 403
In the UN2HDM...
Lagrangian term Couplings
COUPLINGS IN THE UN2HDM
... new decay channels of Z’ become available, giving rise to multiboson signals that may certainly be observed (if they exist)
C ALCULATION OF B RANCHING R ATIOS (BR S )
1. For given benchmarks, ScannerS is used to perform parameter scans and check whether each scanned point is allowed or excluded at approximately 95% confidence level. The constraints taken into account by ScannerS are:
Note:
For more information about ScannerS, refer to
M. Muhlleitner et al.; Eur.Phys.J.C 82 (2022) 3
C ALCULATION OF B RANCHING R ATIOS (BR S )
1. For given benchmarks, ScannerS is used to perform parameter scans and check whether each scanned point is allowed or excluded at approximately 95% confidence level. The constraints taken into account by ScannerS are:
Note:
For more information about ScannerS, refer to
M. Muhlleitner et al.; Eur.Phys.J.C 82 (2022) 3
• Theoretical constraints imposed by perturbative unitarity, boundedness from below and vacuum stability conditions;
C ALCULATION OF B RANCHING R ATIOS (BR S )
1. For given benchmarks, ScannerS is used to perform parameter scans and check whether each scanned point is allowed or excluded at approximately 95% confidence level. The constraints taken into account by ScannerS are:
Note:
For more information about ScannerS, refer to
M. Muhlleitner et al.; Eur.Phys.J.C 82 (2022) 3
• Theoretical constraints imposed by perturbative unitarity, boundedness from below and vacuum stability conditions;
• Electroweak precision constraints;
C ALCULATION OF B RANCHING R ATIOS (BR S )
1. For given benchmarks, ScannerS is used to perform parameter scans and check whether each scanned point is allowed or excluded at approximately 95% confidence level. The constraints taken into account by ScannerS are:
Note:
For more information about ScannerS, refer to
M. Muhlleitner et al.; Eur.Phys.J.C 82 (2022) 3
• Theoretical constraints imposed by perturbative unitarity, boundedness from below and vacuum stability conditions;
• Electroweak precision constraints;
• Flavour constraints;
C ALCULATION OF B RANCHING R ATIOS (BR S )
1. For given benchmarks, ScannerS is used to perform parameter scans and check whether each scanned point is allowed or excluded at approximately 95% confidence level. The constraints taken into account by ScannerS are:
Note:
For more information about ScannerS, refer to
M. Muhlleitner et al.; Eur.Phys.J.C 82 (2022) 3
• Theoretical constraints imposed by perturbative unitarity, boundedness from below and vacuum stability conditions;
• Electroweak precision constraints;
• Flavour constraints;
• Higgs searches and Higgs measurements (incorporated in ScannerS through interfaces to HiggsBounds and HiggsSignals).
C ALCULATION OF B RANCHING R ATIOS (BR S )
1. For given benchmarks, ScannerS is used to perform parameter scans and check whether each scanned point is allowed or excluded at approximately 95% confidence level. The constraints taken into account by ScannerS are:
2. For all the points found in allowed parameter regions, the Branching Ratios (BRs) of the Z’ boson are calculated. Some more points are excluded in this
step due to limits on , and ;
Note:
For more information about ScannerS, refer to
M. Muhlleitner et al.; Eur.Phys.J.C 82 (2022) 3
• Theoretical constraints imposed by perturbative unitarity, boundedness from below and vacuum stability conditions;
• Electroweak precision constraints;
• Flavour constraints;
• Higgs searches and Higgs measurements (incorporated in ScannerS through interfaces to HiggsBounds and HiggsSignals).
C ALCULATION OF B RANCHING R ATIOS (BR S )
1. For given benchmarks, ScannerS is used to perform parameter scans and check whether each scanned point is allowed or excluded at approximately 95% confidence level. The constraints taken into account by ScannerS are:
3. In the analysis of signals that might arise from Z’ decays into scalars, the latter’s BRs are obtained from N2HDECAY (also incorporated in ScannerS).
2. For all the points found in allowed parameter regions, the Branching Ratios (BRs) of the Z’ boson are calculated. Some more points are excluded in this
step due to limits on , and ;
Note:
For more information about ScannerS, refer to
M. Muhlleitner et al.; Eur.Phys.J.C 82 (2022) 3
• Theoretical constraints imposed by perturbative unitarity, boundedness from below and vacuum stability conditions;
• Electroweak precision constraints;
• Flavour constraints;
• Higgs searches and Higgs measurements (incorporated in ScannerS through interfaces to HiggsBounds and HiggsSignals).
S CANNER S – I NPUT PARAMETERS
Scalar masses
125.09 GeV (Benchmarks) VEV parameter
[0 , 20]
Effective couplings of SM Higgs boson
[0.9 , 1.0]
[0.8 , 1.2]
CP-even scalars mixing matrix
{-1 , 1}
[-1 , 1]
U(1)’ parameters
2 TeV 0.9
S CANNER S – I NPUT PARAMETERS
Scalar masses
125.09 GeV (Benchmarks) VEV parameter
[0 , 20]
Effective couplings of SM Higgs boson
[0.9 , 1.0]
[0.8 , 1.2]
CP-even scalars mixing matrix
{-1 , 1}
[-1 , 1]
U(1)’ parameters
2 TeV 0.9
• Together, those parameters allow us to calculate the mixing angles of CP-even scalars;
• It is simultaneously ensured that the SM Higgs boson has SM-like couplings to top quarks and SM gauge bosons.
S CANNER S – I NPUT PARAMETERS
Scalar masses
125.09 GeV (Benchmarks) VEV parameter
[0 , 20]
Effective couplings of SM Higgs boson
[0.9 , 1.0]
[0.8 , 1.2]
CP-even scalars mixing matrix
{-1 , 1}
[-1 , 1]
U(1)’ parameters
2 TeV 0.9
• We consider a UN2HDM with vector-like leptons, so ;
• With this set of parameters:
B ENCHMARKS - O VERVIEW
Benchmark 1:
Benchmark 2:
Benchmark 3:
[30 , 1000] GeV [500 , 700] GeV
[80 , 1000] GeV [90 , 110] GeV
[20 , 40] GeV
[80 , 1000] GeV [250 , 1000] GeV
[200 , 300] GeV [150 , 250] GeV
B ENCHMARK 1
The limits represented in the plots do not exclude the region with
highest .
B ENCHMARK 1
Some points have close to 1, while assumes
values between 0.2 and 0.3. A quadriboson signal might be produced in these conditions.
B ENCHMARK 2
Most of this parameter region is still allowed by the limits shown on the plots.
B ENCHMARK 2
The decays of both scalars can have a BR close to one while the Z’ decay is above 0.2. Triboson or even quadriboson signals might arise in this benchmark.
B ENCHMARK 3
Most points are still allowed by the limits represented on the plots.
B ENCHMARK 3
As in benchmark 2, triboson or quadriboson signals can be observed in this benchmark.
• The UN2HDM extends the the SM gauge group with an additional U(1)’
group, leading to to the existence of a new gauge boson Z’ that is assumed to be much heavier than SM particles;
C ONCLUDING R EMARKS
• The UN2HDM extends the the SM gauge group with an additional U(1)’
group, leading to to the existence of a new gauge boson Z’ that is assumed to be much heavier than SM particles;
• Its scalar sector with two complex scalar doublets and one complex scalar singlet gives rise to cascade decays initiated by decays of Z’ that could not be observed, for example, in the MSBM;
C ONCLUDING R EMARKS
• The UN2HDM extends the the SM gauge group with an additional U(1)’
group, leading to to the existence of a new gauge boson Z’ that is assumed to be much heavier than SM particles;
• Its scalar sector with two complex scalar doublets and one complex scalar singlet gives rise to cascade decays initiated by decays of Z’ that could not be observed, for example, in the MSBM;
• Some parameter regions of the UN2HDM accommodate, simultaneously, sizeable BRs of new decay channels of Z’ into scalars and predominant decays of the latter into bosons. This leads to the existence of multiboson signals with BRs that may allow their observation at the LHC.
C ONCLUDING R EMARKS
• The UN2HDM extends the the SM gauge group with an additional U(1)’
group, leading to to the existence of a new gauge boson Z’ that is assumed to be much heavier than SM particles;
• Its scalar sector with two complex scalar doublets and one complex scalar singlet gives rise to cascade decays initiated by decays of Z’ that could not be observed, for example, in the MSBM;
• Some parameter regions of the UN2HDM accommodate, simultaneously, sizeable BRs of new decay channels of Z’ into scalars and predominant decays of the latter into bosons. This leads to the existence of multiboson signals with BRs that may allow their observation at the LHC.
Thank you!
C ONCLUDING R EMARKS
