Measurements of Transverse Energy Flow in Deep-Inelastic Scattering at HERA

TL;DR

This study measures the transverse energy flow ET* in neutral current deep-inelastic scattering at HERA, using the H1 detector to cover a wide kinematic range in $Q^2$, $x$, and $W$ and extending pseudorapidity reach into the proton remnant region. ET* is analyzed in the hadronic center-of-mass frame and as a function of $ ilde ext{eta}$, with detailed comparisons to a suite of QCD-based models that implement DGLAP, BFKL, and CCFM evolutions, as well as direct and resolved virtual-photon processes. The results show a central ET* rise with decreasing $x$ and with increasing $W$, and a high-$Q^2$ peak in ET* that aligns with the Breit frame origin, with several models providing reasonable descriptions while others reveal specific shortcomings in central or remnant regions. The findings demonstrate the sensitivity of hadronic final-state observables to parton shower dynamics, photon structure, and hadronisation, informing ongoing developments in QCD modeling for DIS final states.

Abstract

Measurements of transverse energy flow are presented for neutral current deep-inelastic scattering events produced in positron-proton collisions at HERA. The kinematic range covers squared momentum transfers Q^2 from 3.2 to 2,200 GeV^2, the Bjorken scaling variable x from 8.10^{-5} to 0.11 and the hadronic mass W from 66 to 233 GeV. The transverse energy flow is measured in the hadronic centre of mass frame and is studied as a function of Q^2, x, W and pseudorapidity. A comparison is made with QCD based models. The behaviour of the mean transverse energy in the central pseudorapidity region and an interval corresponding to the photon fragmentation region are analysed as a function of Q^2 and W.

Figures (8)

• Figure 1: The distribution of $p_T^h/p_T^e$ measured with the 1994 nominal vertex data-set (left), the 1994 shifted vertex data-set (middle) and the 1996 data-set (right). The data are compared with predictions from Django.
• Figure 2: The inclusive transverse energy flow $1/Nd{\hbox{$E_T^*$}} /d\eta^*$ at different values of $x$ and $Q^2$ for the low $Q^2$ sample. Note that the errors on all of the measurements made at the two lowest values of $\eta^*$ in each $x$ and $Q^2$ interval are highly correlated and largely independent of the errors at larger values of $\eta^*$. The data are compared to four QCD based models. The arrows mark the average position of the origin of the Breit frame ($\frac{1}{2}\ln{\frac{1}{{\langle}x{\rangle}}-1}$).
• Figure 3: The inclusive transverse energy flow $1/Nd{\hbox{$E_T^*$}} /d\eta^*$ at different values of $x$ and $Q^2$ for the high $Q^2$ sample. The data are compared to four QCD based models. The arrows mark the average position of the origin of the Breit frame ($\frac{1}{2}\ln{\frac{1}{{\langle}x{\rangle}}-1}$).
• Figure 4: The inclusive transverse energy flow $1/Nd{\hbox{$E_T^*$}} /d\eta^*$ for two selected kinematic bins from Figs. \ref{['lpl']} and \ref{['gpl']}. The influence of GAL string reinteractions and parton showers on the expected transverse energy flow are shown.
• Figure 5: Variation of mean $E_T^*$ in the central pseudorapidity region ($-0.5<\eta^*<0.5$) with $x$ in different regions of $Q^2$ compared to four QCD based models and an analytical BFKL calculation.