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62 lines
3.3 KiB
62 lines
3.3 KiB
\midheading{Dark Matter Processes Mono-jet and Mono-photon 800-848}
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\textbf{This process is currently only officially supported with version 8.0 and earlier, use at your own risk!}
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This section provides an overview of the Dark Matter (DM) processes
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available in MCFM. For more details on this calculation, please see Ref.~\cite{Fox:2012ru}.
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Since these processes are quite different in the
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range of possible input parameters (reflecting the range of potential
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BSM operators) the majority of the new features are controlled by the
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file {\tt dm\_parameters.DAT} located in the {\tt Bin} directory. We
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begin this section by describing the inputs in this file. Note that
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these processes are still controlled, as usual by {\tt input.ini}
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which is responsible for selecting the process, order in perturbation
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theory, PDFs and phase space cuts etc. The new file controls only the
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new BSM parameters in the code.
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\begin{itemize}
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\item
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{\tt [dm mass]} This parameter sets the mass of the dark matter particle $m_{\chi}$.
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\item
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{\tt [Lambda]} Controls the mass scale associated with the suppression of the higher dimensional operator in the
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effective theory approach. Note that each
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operator has a well defined scaling with respect to Lambda, so cross sections and distributions obtained with one
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particular value can be readily extended to
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determine those with different $\Lambda$.
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\item
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{\tt [effective theory] } Is a logical variable which controls whether or not the effective field theory is used in the
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calculation of the DM process. If this value is set to
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{\tt .false.} then one must specify the mass of the light mediator and its width (see below for more details).
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\item
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{\tt [Yukawa Scalar couplings]} Is a logical variable which determines if the scalar and pseudo scalar operators scale
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with the factor $m_{q}/\Lambda$ ( {\tt. .true.})
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or 1 ({\tt .false.}).
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\item
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{ \tt [Left handed DM couplings] } and { \tt [Right handed DM couplings] }
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These variables determine the coupling of the
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various flavours of quarks to the DM operators. The default value is 1.
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Note that the code uses the fact that vector operators scale as
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$(L+R)$ and axial operators scale as $(L-R)$ in constructing cross
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sections. Therefore you should be careful if modifying these
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parameters. For the axial and pseudo scalar operators the code will
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set the right-handed couplings to be the negative of the left handed
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input couplings (if this is not already the case from the setup) and
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inform the user it has done so. The most likely reason to want to
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change these values is to inspect individual flavour operators
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separately, i.e.\ to investigate an operator which only couples to up
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quarks one would set all couplings to 0d0 apart from {\tt [up type]}
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which would be left as 1d0.
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\item
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{\tt [mediator mass]} If {\tt [effective theory]} is set to {\tt .false.} this variable controls the mass of the
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mediating particle.
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\item
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{\tt [mediator width]} If {\tt [effective theory]} is set to {\tt .false.} this variable controls the width of the
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mediating particle
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\item
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{\tt [g\_x]} If {\tt [effective theory]} is set to {\tt .false.} this variable controls the coupling of the mediating
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particle to the DM.
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\item
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{\tt [g\_q]} If {\tt [effective theory]} is set to {\tt .false.} this variable controls the coupling of the mediating
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particle to the quarks.
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\end{itemize}
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