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VPolar
: The Standard Model at NLO in QCD with helicity-polarized W and Z bosons
Contact Author
Richard Ruiz
- Institute of Nuclear Physics Polish Academy of Science (IFJ PAN)
- rruiz AT ifj.edu.pl
In collaboration with:
- Javurkova, R.C.L. de Sá, and J. Sandesara arXiv:2401.17365 [ 1 ]
- Buarque Franzosi, O. Mattelaer, and Sujay Shil arXiv:1912.01725 [ 2 ]
Usage resources
- For instructions and examples on using the VPolar UFO libraries, see M. Javurkova, et al, arXiv:2401.17365 [ 1 ]
- For additional background, see also D. Buarque Franzosi, et al, arXiv:1912.01725 [ 2 ]
- See Validation section below for additional information
- Special note: this UFO was developed using MG5aMC and calls the 1L, 1T, and 1A propagators defined in ALOHA (see aloha_object.py and create_aloha.py). These may be defined differently in other generators. If they are not defined in your favorite generators, they must be added to the propagators.py file in the
VPolar
UFO. The file particles.py must then be updated to reflect the propagator names. R. Ruiz is happy to assist with this.
Citation requests
- If using the UFO, please cite , see M. Javurkova, et al, arXiv:2401.17365 [ 1 ]
Model Description -- helicity polarization as a Feynman rule
The broad idea of the helicity polarization as a Feynman rule is to treat the helicity-truncated propagator (see [ 2 ] for details) as the Feynman rule for a particle that sits in a definite helicity polarization. The helicity-truncated propagator is given by
\begin{align} \Pi_{\mu\nu}^{V\lambda}(q) = \frac{-i\varepsilon_\mu(q,\lambda)\ \varepsilon^*_\nu(q,\lambda)}{q^2-M_V^2 +iM_V\Gamma_V} \end{align} and is related to the full propagator by \begin{align} &\Pi_{\mu\nu}^V (q) = \frac{-i\left(g_{\mu\nu} - q_\mu q_\nu / M_V^2\right)}{q^2-M_V^2 +iM_V\Gamma_V}\ \\ &=\sum_{\lambda\in\{0,\pm1,A\}} \eta_\lambda\ \left( \frac{-i\varepsilon_\mu(q,\lambda)\ \varepsilon^*_\nu(q,\lambda)}{q^2-M_V^2 +iM_V\Gamma_V} \right)\ . \end{align}
Here, $\eta_\lambda=+1$
, unless $\lambda=0$
and $V_{\lambda}$
is in the t-channel; in that case $\eta_\lambda=-1$
.
By making the graphical identification
then one can interpret the full propagator in Eq. 3 as the sum of propagators (or interfering graphs) for a collection of particles $V_\lambda$
, where each $V_\lambda$
has its own propagator.
The VPolar
UFOs implement this idea for the W and Z bosons.
UFO Description and Usage
ZPolar
- The
SM_Loop_ZPolar
UFO contains the SM Lagrangian and includes QCD counter terms up to NLO in QCD. (This means it can be used for both tree-level computations and loop-level computations up to one loop in QCD.) Importantly, the SM Z boson has been replaced with the longitudinal stateZ0
, the transverse stateZT
, the auxiliary stateZA
, and the unpolarized stateZX
. The stateZX
is essentially the original Z boson.- The PIDs are: 23 for
ZX
, 230 forZ0
, 231 forZT
, and 232 forZA
- The W boson is NOT polarized in this UFO
- ~/Path $ wget http://feynrules.irmp.ucl.ac.be/raw-attachment/wiki/VPolarization/SM_Loop_ZPolar.tgz ./
- ~/Path $ tar -zxvf SM_Loop_ZPolar.tgz
- The PIDs are: 23 for
WPolar
- The
SM_Loop_WPolar
UFO is likeSM_Loop_ZPolar
but for the W boson- The PIDs are: +24 for
WX^+
, +240 forW0^+
, +241 forWT^+
, and +242 forWA^+
- For the
W^-
fields, use-PID
- The Z boson is NOT polarized in this UFO
- ~/Path $ wget http://feynrules.irmp.ucl.ac.be/raw-attachment/wiki/VPolarization/SM_Loop_WPolar.tgz ./
- ~/Path $ tar -zxvf SM_Loop_WPolar.tgz
- The PIDs are: +24 for
LO UFOs
- The
SM_WPolar_XLO
andSM_ZPolar_XLO
UFOs are like the two UFOs above but DO NOT CONTAIN QCD counter terms
- The
SM_VPolar_XLO
UFO contains both polarized W and Z bosons but DOES NOT CONTAIN QCD counter terms
Usage in MG5aMC@NLO
For usage in MadGraph5aMC@NLO, see the appendix of M. Javurkova, et al, arXiv:2401.17365 [ 1 ].
Studies that have used the above model files
- Please email to update this space.
References
[1] M. Javurkova, R. Ruiz, R. Coelho Lopes de Sa, and J. Sandesara, Polarized ZZ pairs in gluon fusion and vector boson fusion at the LHC, arXiv:2401.17365
[2] D. Buarque Franzosi, O. Mattelaer, R. Ruiz, S. Shil, Automated Predictions from Polarized Matrix Elements, JHEP 2020, 82 (2020) arXiv:1912.01725
Attachments (14)
-
SM_ZPolar_XLO.tgz
(16.5 KB
) - added by 10 months ago.
leading order UFO for Z with polarization [tarball]
-
SM_WPolar_XLO.tgz
(19.1 KB
) - added by 10 months ago.
leading order UFO for W with polarization [tarball]
-
SM_Loop_ZPolar.tgz
(22.8 KB
) - added by 10 months ago.
next-to-leading order in QCD UFO for Z with polarization [tarball]
-
SM_Loop_WPolar.tgz
(25.6 KB
) - added by 10 months ago.
next-to-leading order in QCD UFO for W with polarization [tarball]
-
sm_loop_wpolar.fr
(29.3 KB
) - added by 10 months ago.
FeynRules model file for W with polarization
-
sm_loop_zpolar.fr
(28.8 KB
) - added by 10 months ago.
FeynRules model file for Z with polarization
-
sm_loop_vpolar.fr
(32.1 KB
) - added by 10 months ago.
FeynRules model file for W and Z with polarization
-
mgPolar_FeynmanRule.png
(35.5 KB
) - added by 10 months ago.
mgPolar_FeynmanRule
-
SM_VPolar_XLO.tgz
(28.9 KB
) - added by 10 months ago.
leading order in QCD UFO for W and Z with polarization [tarball]
-
SM_Loop_VPolar.tgz
(36.2 KB
) - added by 10 months ago.
next-to-leading order in QCD UFO for W and Z with polarization [tarball]
-
sm_loop_vpolar_public.nb
(120.1 KB
) - added by 10 months ago.
Mathematica notebook for generating UFOs
-
2023_0201_SM_Loop_VPolar_FA.nlo
(140.4 KB
) - added by 10 months ago.
output from WriteCT function (NLOCT)
-
SM_Loop_ZPolar_Gen3.tgz
(25.3 KB
) - added by 6 weeks ago.
Loop ZPolar with all generation III masses
-
SM_ZPolar_Gen3_XLO.tgz
(17.1 KB
) - added by 6 weeks ago.
XLO ZPolar with all generation III masses
Download all attachments as: .zip