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83 lines
4.3 KiB
83 lines
4.3 KiB
Note that all the photon cuts specified in this section of the input file, are applied even if {\tt makecuts} is set to {\tt .false.}.
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\begin{longtable}{p{3.5cm}p{12cm}}
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\hline
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\multicolumn{1}{c}{{\textbf{Section} \texttt{photon}}} & \multicolumn{1}{c}{{\textbf{Description}}} \\
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\hline
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{\tt fragmentation} & This parameter is a logical variable that determines whether the production of photons
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by a parton
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fragmentation process is included. If {\tt fragmentation} is set to {\tt .true.}, the code uses a standard
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cone isolation
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procedure (that includes LO fragmentation contributions in the NLO calculation).
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If {\tt fragmentation} is set to {\tt .false.}, the code implements
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a Frixione-style photon cut~\cite{Frixione:1998jh},
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\begin{equation}
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\sum_{i \in R_0} E_{T,i}^j < \epsilon_h E_{T}^{\gamma} \bigg(\frac{1-\cos{R_{i\gamma}}}{1-\cos{R_0}}\bigg)^{n}
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\;.
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\label{frixeq}
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\end{equation}
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In this equation, $R_0$, $\epsilon_h$ and $n$ are defined by {\tt cone\_ang}, {\tt epsilon\_h}
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and {\tt n\_pow} respectively (see below).
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$E_{T,i}^{j}$ is the transverse energy of a parton, $E_{T}^\gamma$ is the
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transverse energy of the photon and $R$ is the separation between the photon and the parton using the
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usual definition
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\begin{equation}
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R=\sqrt{\Delta\phi_{i\gamma}^2+\Delta\eta_{i\gamma}^2} \,.
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\end{equation}
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$n$ is an integer parameter which by default is set to~1. \\
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{\tt fragmentation\_set} & A length eight character variable that is used to choose the particular photon
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fragmentation set.
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Currently implemented fragmentation functions can be called with `{\tt BFGSet\_I}', `{\tt
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BFGSetII}'~\cite{Bourhis:1997yu} or `{\tt GdRG\_\_LO}'~\cite{GehrmannDeRidder:1998ba}. \\
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{\tt fragmentation\_scale} & A double precision variable that will be used to choose the scale
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at which the photon fragmentation is evaluated. \\
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{\tt gammptmin} & This specifies the value
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of $p_T^{\mathrm{min}}$ for the photon with the largest transverse momentum.
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Note that this cut, together with all the photon cuts specified in this section
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of the input file, are applied even if {\tt makecuts} is set to {\tt .false.}.
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One can also add an entry for \texttt{gammptmax} to cut on a range. \\
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{\tt gammrapmax} & This specifies the value
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of $|y|^{\mathrm{max}}$ for any photons produced in the process. One can also add an entry
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for \texttt{gammrapmin} to cut on a range. \\
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{\tt gammpt2}, {\tt gammpt3} & The values
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of $p_T^{\mathrm{min}}$ for the second and third photons, ordered by $p_T$. \\
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{\tt Rgalmin} & Using the usual definition of $R$ above,
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this requires that all photon-lepton pairs are separated by
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$R >$~{\tt Rgalmin}. This parameter must be non-zero
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for processes in which photon radiation from leptons is included. \\
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{\tt Rgagamin} & Using the usual definition of $R$ above,
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this requires that all photon pairs are separated by
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$R >$~{\tt Rgagamin}. \\
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{\tt Rgajetmin} & Using the usual definition of $R$ above,
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this requires that all photon-jet pairs are separated by
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$R >$~{\tt Rgajetmin}. \\
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{\tt cone\_ang} & Fixes the cone size ($R_0$) for photon isolation.
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This cone is used in both forms of isolation. \\
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{\tt epsilon\_h} & This cut controls the amount of radiation allowed in cone when {\tt fragmentation} is set
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to
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{\tt .true.}. If {\tt epsilon\_h} $ < 1$ then the photon is isolated using
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$\sum_{\in R_0} E_T{\mathrm{(had)}} < \epsilon_h \, p^{\gamma}_{T}.$ Otherwise {\tt epsilon\_h} $ > 1$ sets
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$E_T(max)$ in $\sum_{\in R_0} E_T{\mathrm{(had)}} < E_T(max)$. \\
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{\tt n\_pow} & When using the Frixione isolation prescription, the exponent $n$ in Eq.~(\ref{frixeq}). \\
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{\tt fixed\_coneenergy} & This is only operational when using the Frixione isolation prescription.
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If {\tt fixed\_coneenergy} is .false. then $\epsilon_h$ controls the amount of hadronic energy allowed
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inside the cone using the
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Frixione isolation prescription (see above, Eq.~(\ref{frixeq}))
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If {\tt fixed\_coneenergy} is .true. then this formula
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is replaced by one where $\epsilon_h E_T^\gamma \rightarrow \epsilon_h$. \\
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{\tt hybrid}, {\tt R\_inner} & If {\tt hybrid} is set to .true. use a hybrid isolation scheme
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with Frixione isolation on an inner cone of radius {\tt R\_inner}. \\
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\hline
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\end{longtable}
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