Loopholes in W R Searches at the LHC
Özer Özdal
Abstract We present mass bounds of the W R gauge boson in generic left-right
symmetric models. Assuming that the gauge bosons couple universally to quarks
and leptons, we allow different gauge couplings g R = g L and mass mixing,
V L
CKM = V R
CKM in the left and right sectors. We investigate scenarios where W R
is lighter, or heavier than the right-handed neutrino ν R . In these scenarios, W R
mass bounds can be considerably relaxed, while Z R mass bounds are much more
stringent. In the case where M W R ≤ M ν R , the experimental constraints come from
W R → tb and W R → jj channels, while if M W R ≥ M ν R , the dominant constraints
come from W R → jj . Our results show that W R mass bounds can be relaxed
significantly.
Keywords Left-right symmetric models · Exclusion limits for heavy
right-handed W boson
Left-right symmetric models (LRSMs) [1–3] provide a natural explanation for
neutrino masses without resorting to higher scales. Based on the SU (2) L ⊗
SU (2) R ⊗ U(1) B−L , these models restore parity symmetry, which is conserved
at high energy, and spontaneously broken at some energy scale connected to the
SU (2) R breaking scale [4]. Small neutrino masses are induced by heavy (and
most often, Majorana) right-handed neutrinos through the phenomena known as
the seesaw mechanism [5, 6]. Within the framework described here both Type I and
Type II seesaw mechanisms can be naturally imbedded in the model.
In making any specific predictions, there are several sources of uncertainty in
the model. The most important source of uncertainty comes from the right-handed
quark mixing matrix, similar to that of the left-handed quark Cabibbo–Kobayashi–
Maskawa (CKM) mixing. It is also commonly assumed that left-right symmetry
imposes g L = g R . If breaking of SU (2) R ⊗ U(1) B−L occurs at a high scale, at that
Ö. Özdal ()
Department of Physics, Concordia University, Montreal, QC, Canada
e-mail: ozer.ozdal@concordia.ca
© Springer Nature Switzerland AG 2021
M. B. Paranjape et al. (eds.), Quantum Theory and Symmetries, CRM Series in
Mathematical Physics, https://doi.org/10.1007/978-3-030-55777-5_55
587
Özer Özdal
Abstract We present mass bounds of the W R gauge boson in generic left-right
symmetric models. Assuming that the gauge bosons couple universally to quarks
and leptons, we allow different gauge couplings g R = g L and mass mixing,
V L
CKM = V R
CKM in the left and right sectors. We investigate scenarios where W R
is lighter, or heavier than the right-handed neutrino ν R . In these scenarios, W R
mass bounds can be considerably relaxed, while Z R mass bounds are much more
stringent. In the case where M W R ≤ M ν R , the experimental constraints come from
W R → tb and W R → jj channels, while if M W R ≥ M ν R , the dominant constraints
come from W R → jj . Our results show that W R mass bounds can be relaxed
significantly.
Keywords Left-right symmetric models · Exclusion limits for heavy
right-handed W boson
Left-right symmetric models (LRSMs) [1–3] provide a natural explanation for
neutrino masses without resorting to higher scales. Based on the SU (2) L ⊗
SU (2) R ⊗ U(1) B−L , these models restore parity symmetry, which is conserved
at high energy, and spontaneously broken at some energy scale connected to the
SU (2) R breaking scale [4]. Small neutrino masses are induced by heavy (and
most often, Majorana) right-handed neutrinos through the phenomena known as
the seesaw mechanism [5, 6]. Within the framework described here both Type I and
Type II seesaw mechanisms can be naturally imbedded in the model.
In making any specific predictions, there are several sources of uncertainty in
the model. The most important source of uncertainty comes from the right-handed
quark mixing matrix, similar to that of the left-handed quark Cabibbo–Kobayashi–
Maskawa (CKM) mixing. It is also commonly assumed that left-right symmetry
imposes g L = g R . If breaking of SU (2) R ⊗ U(1) B−L occurs at a high scale, at that
Ö. Özdal ()
Department of Physics, Concordia University, Montreal, QC, Canada
e-mail: ozer.ozdal@concordia.ca
© Springer Nature Switzerland AG 2021
M. B. Paranjape et al. (eds.), Quantum Theory and Symmetries, CRM Series in
Mathematical Physics, https://doi.org/10.1007/978-3-030-55777-5_55
587