# A phenomenological investigation of the integral and the differential versions of the Kimber-Martin$-Ryskin $unintegrated$ parton distribution functions using two different constraints and the MMHT2014 PDF

## TL;DR

This study compares integral and differential versions of the Kimber-Martin-Ryskin unintegrated parton distribution functions using different constraints and PDFs, finding the integral approach aligns better with experimental data.

## Contribution

It introduces a detailed comparison of UPDF behaviors with various PDFs and constraints, highlighting the effectiveness of the integral prescription in matching experimental results.

## Key findings

- Integral prescription of KMR UPDF agrees well with experimental data.
- Differential version with cutoff-independent PDFs deviates from data.
- Small-x region shows increased PSF and PLSF due to gluon excess.

## Abstract

We previously investigated the compatibility of the $Kimber$-$Martin$-$Ryskin$ ($KMR$) $unintegrated$ parton distribution functions ($UPDF$) with the experimental data on the proton (longitudinal) structure functions ($PSF$ ($PLSF$)). Recently $Golec-Biernat$ and $Stasto$ ($GBS$) demonstrated that the differential version of $KMR$ prescription and the implementations of angular (strong) ordering ($AOC$ ($SOC$)) constraints, cause the negative-discontinuous $UPDF$ with the ordinary parton distribution functions ($PDF$) as the input, which leads to a sizable effect on the calculation of $PSF$. In the present work, we use the new $MMHT2014$-$LO$-$PDF$ as the input and focus on the $UPDF$ behaviors as was raised by $GBS$. The resulting $PSF$ and $PLSF$ are compared with the $MSTW2008$-$LO$-$PDF$ and $MRST99$-$PDF$ and the 2014 data given by the $ZEUS$ and $H1$ collaborations. The calculated $PSF$ and $PLSF$ based on the integral prescription of the $KMR$-$UPDF$ with the $AOC$ and the ordinary $PDF$ as the input are reasonably consistent with the experimental data. Therefore, they are approximately independent to the $PDF$ (no need to impose cutoff on the $PDF$). At very small $x$ regions because of the excess of gluons in the $MMHT2014$-$LO$-$PDF$ and $MSTW2008$-$LO$-$PDF$, an increase in $PSF$ and $PLSF$ is achieved. Finally, according to the $GBS$ report the differential version by using the cutoff independent $PDF$ produces results far from the experimental data.