Add user docs

docs/index.md

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 ## User Guide
 
+- [Workflow overview](./user/workflow.md)
 - [Conda Environments](./user/conda_environments.md)
 - [Releases](./releases.md)
 

docs/user/event_processing.md

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+# Event processing
+The BL4B instrument leverages the concept of weighted events for several aspects of
+the reduction process. Following this approach, each event is treated separately and is
+assigned a weigth $w$ to accound for various corrections. Summing events then becomes the
+sum of the weights for all events.
+
+## Loading events and dead time correction
+A dead time correction is available for rates above around 2000 counts/sec. Both
+paralyzing and non-paralyzing implementation are available. Paralyzing refers to a detector
+that extends its dead time period when events occur while the detector is already unavailable
+to process events, while non-paralyzing refers to a detector that always becomes available
+after the dead time period [1].
+
+The dead time correction to be multiplied by the measured detector counts is given by
+the following for the paralyzing case:
+
+$$
+C_{par} = -{\cal Re}W_0(-R\tau/\Delta_{TOF}) \Delta_{TOF}/R
+$$
+where $R$ is the number of triggers per accelerator pulse within a time-of-flight bin $\Delta_{TOF}$.
+The dead time for the current BL4B detector is $\tau=4.2$ $\mu s$. In the equation avove, ${\cal Re}W_0$ referes to the principal branch of the Lambert W function.
+
+The following is used for the non-paralyzing case:
+$$
+C_{non-par} = 1/(1-R\tau/\Delta_{TOF})
+$$
+
+By default, we use a paralyzing dead time correction with $\Delta_{TOF}=100$ $\mu s$. These parameters can be changed.
+
+The BL4B detector is a wire chamber with a detector readout that includes digitization of the
+position of each event. For a number of reasons, like event pileup, it is possible for the 
+electronics to be unable to assign a coordinate to a particular trigger event. These events are
+labelled as error events and stored along with the good events. While only good events are used
+to compute reflectivity, error events are included in the $R$ value defined above. For clarity, we chose to define $R$ in terms of number of triggers as opposed to events.
+
+Once the dead time correction as a function for time-of-flight is computed, each event
+in the run being processed is assigned a weight according to the correction. 
+
+$w_i = C(t_i)$
+
+where $t_i$ is the time-of-flight of event $i$. The value of $C$ is interpolated from the 
+computed dead time correction distribution.
+
+[1] V. Bécares, J. Blázquez, Detector Dead Time Determination and OptimalCounting Rate for a Detector Near a Spallation Source ora Subcritical Multiplying System, Science and Technology of Nuclear Installations, 2012, 240693, https://doi.org/10.1155/2012/240693
+
+
+### Correct for emission time
+Since neutrons of different wavelength will spend different amount of time on average
+within the moderator, a linear approximation is used by the data acquisition system to
+account for emission time when phasing choppers.
+
+The time of flight for each event $i$ is corrected by an small value given by
+
+$\Delta t_i = -t_{off} + t_{mult} * t_i * h L / m_n$
+
+where $h$ is Planck's constant, $m_n$ is the mass of the neutron, and $L$ is the distance
+between the moderator and the detector.
+
+The $t_{off}$, $t_{mult}$, and $L$ parameters are process variables that are stored in the
+data file and can be changed in the data acquisition system.
+
+
+### Gravity correction
+
+
+### Q calculation
+
+### Constant-Q binning
+
+## Normalization options