Beauty Production

Table 3: Overview of the measurements of open beauty production at H1 and ZEUS.

	Analysis	Data	Kinematic Region
			$Q^2$	$y$	Other cuts
			[GeV$^2$]
H1
[36]	$b\rightarrow \mu X$ in $\gamma p$	1996	$<1$	$0.1 ... 0.8$	$35^{\circ}<\theta^\mu<130^{\circ}$    $p_t^\mu>2.0\;$GeV
[44]	$b\bar{b}\rightarrow \mu jj$ in $\gamma p$	99-00	$<1$	$0.2 ... 0.8$	$p_t^{jet\,1\,(2)}>7\,(6)\;$GeV    $\vert\eta^{jet}\vert<2.5$
					$-0.55<\eta^\mu<1.1$   $p_t^\mu>2.5\;$GeV
	$b\rightarrow \mu j$ in DIS	99-00	$2 ... 100$	$0.1...0.7$	$p_{T,jet}^{Breit}>6\;$GeV   $\vert\eta^{jet}\vert<2.5$
					$-0.75<\eta^\mu<1.15$   $p_t^\mu>2.5\;$GeV
[47]	$b\bar{b}\rightarrow D^*\mu$ in $\gamma p$	96-00	$<1$	$0.05 ... 0.75$	$p_t(D^*)>1.5\;$GeV   $\vert\eta(D^*)\vert<1.5$
					$p^\mu>2.0\;$GeV   $\vert\eta^\mu\vert<1.735$
[43]	$F_2^{b}$ at high $Q^2$	99-00	$>150$	$0.07...0.7$
[46]	$F_2^{b}$ at low $Q^2$	99-00	$2...120$	$0.07...0.7$
[45]	dijets in $\gamma p$	99-00	$<1$	$0.15 ... 0.8$	$p_t^{jet_{1(2)}}>11(8)$ GeV   $-0.88 < \eta_{jets} < 1.3$
ZEUS
[39]	$b\bar{b}\rightarrow e jj$ in $\gamma p$	96-97	$<1$	$0.2 ... 0.8$	$E_t^{jet\,1\,(2)}>7\,(6)\;$GeV   $\vert\eta^{jet}\vert<2.4$
					$\vert\eta^{e^-}\vert<1.1$   $p_t^{e^-}>1.6\;$GeV
[40]	$b\bar{b}\rightarrow \mu jj$ in $\gamma p$	96-00	$<1$	$0.2 ... 0.8$	$p_t^{jet\,1\,(2)}>7\,(6)\;$GeV   $\vert\eta^{jet}\vert<2.5$
					$-1.6<\eta^{\mu}<1.3$ $p^{\mu}>2.5\;$GeV
					or: $1.48<\eta^{\mu}<2.3$ $p^{\mu}>1(4)$ GeV
[41]	$b\bar{b}\rightarrow \mu j$ in DIS	99-00	$>2$	$0.05 ... 0.7$	$E_{T,\, jet}^{Breit}>6\;$GeV   $-2<\eta^{lab}_{jet}<2.5$
					( $-0.9<\eta^{\mu}<1.3$   $p_t^{\mu}>2.0\;$GeV)
					or: ( $-1.6<\eta^{\mu}<-0.9$ $p^\mu>2.0\;$GeV)
[48]	$b\bar{b}\rightarrow D^*\mu$	96-00	$<1$	$0.05...0.85$	$p_t^{D^*}>1.9$   $\vert\eta_{D^*}\vert<1.5$
			$>2$	$0.05 ... 0.7$	$p_t^{\mu}>1.4$ GeV   $-1.75<\eta_{\mu}<1.3$
[42]	$b\bar{b}\rightarrow \mu\mu$	96-00			$-2.2<\eta_{\mu}<2.5$       $p_t^{\mu_1}>1.5$ GeV
					$p_t^{\mu_2}>1.8$ GeV for $\eta<0.6$
					$p^{\mu_2}>2.5$ GeV or $p_t^{\mu_2}>1.5$ GeV for $\eta>0.6$

For beauty production, theoretical calculations in perturbative quantum chromodynamics are expected to give predictions that are more reliable than for charm, as the mass $m_b$ of the $b$ quark ( $\,m_b \sim$ 5 GeV) provides an energy scale in a region in which perturbative approaches have been successful in describing the data.

Experimentally, measurements of beauty production are somewhat more challenging than measurements of charm production because the beauty cross sections and branching ratios are significantly smaller than those of charm. Consequently, the explicit reconstruction of hadronic resonances containing beauty is not viable at HERA, due to lack of statistics. The measurements preformed at the HERA experiments H1 and ZEUS make use of semi-leptonic decays of beauty hadrons and, in more recent analyses, lifetime distributions have been used to distinguish beauty from charm and light quark events (see also section 5.5). In table 3 an overview of the measurements of beauty production performed at HERA is given.

The first measurements of the beauty cross section at HERA [36,39] were higher than pQCD predictions, calculated at next-to-leading order. Similar observations were made in hadron-hadron collisions [160] and also in two-photon interactions [161].