On the intrinsic bottom content of the nucleon and its impact on heavy new physics at the LHC

Abstract

Heavy quark parton distribution functions (PDFs) play an important role in several Standard Model and New Physics processes. Most analyses rely on the assumption that the charm and bottom PDFs are generated perturbatively by gluon splitting and do not involve any non-perturbative degrees of freedom. It is clearly necessary to test this hypothesis with suitable QCD processes. Conversely, a non-perturbative, intrinsic heavy quark parton distribution has been predicted in the literature. We demonstrate that to a very good approximation the scale-evolution of the intrinsic heavy quark content of the nucleon is governed by non-singlet evolution equations. This allows us to analyze the intrinsic heavy quark distributions without having to resort to a full-fledged global analysis of parton distribution functions. We exploit this freedom to model intrinsic bottom distributions which are so far missing in the literature in order to estimate the impact of this non-perturbative contribution to the bottom-quark PDF, and on parton-parton luminosities at the LHC. This technique can be applied to the case of intrinsic charm, albeit within the limitations outlined in the following.

LHCb anomalies from a natural perspective

“…figure 8. (a) in [58]). As a result, even though the coupling of the lightest KK-mode to bb pairs is enhanced by a factor of √ 2, the total production cross section compared to that of a Z with the same couplings as those of the SM Z is smaller by a factor ∼ 10 −3 .…”

LHC and its impact on nCTEQ15 PDFs

“…4 We have added CTEQ6.1+EPS09 as CTEQ6.1 was the baseline used for the EPS09 fit. 5 While the charm PDF does play a role in the above (the bottom contribution is minimal), c(x) is generated radiatively by the process g → cc (we assume no intrinsic component) [12]; thus, it is essentially determined by the charm mass value and the gluon PDF. In contrast, the "intrinsic" nature of the strange PDF leads to its comparably large uncertainties.…”

Intrinsic bottom and its impact on heavy new physics at the LHC

“…Moreover, for the case of intrinsic bottom which is additionally suppressed, the accuracy of the approximation will be even better. For completeness we also provided similar validation using the parton-parton luminosities in [10] to which we refer the reader for further details. …”

“…In this contribution, we summarize a technique introduced in [10] which can provide IB PDFs for any generic non-IB PDF set. This approach relies on the fact that the intrinsic bottom PDF evolves (to an excellent precision) according to a standalone non-singlet evolution equation.…”