Searching for intrinsic charm in the proton at the LHC

Abstract

Despite rather long-term theoretical and experimental studies, the hypothesis of the non-zero intrinsic (or valence-like) heavy quark component of the proton distribution functions has not yet been confirmed or rejected. The LHC with $pp$-collisions at $\sqrt{s}=$ 7--14 TeV will obviously supply extra unique information concerning the above-mentioned component of the proton. To use the LHC potential, first of all, one should select the parton-level (sub)processes (and final-state signatures) that are most sensitive to the intrinsic heavy quark contributions. To this end inclusive production of $c(b)$-jets accompanied by photons is considered. On the basis of the performed theoretical study it is demonstrated that the investigation of the intrinsic heavy quark contributions looks very promising at the LHC in processes such as $pp\rightarrow \gamma+ c(b)+X$.Comment: 13 pages, 6 figure

Search for intrinsic charm in vector boson production accompanied by heavy-flavor jets

“…Intrinsic charm and beauty contribution to protons in W/Z plus heavy flavor jets at the LHC At the LHC, with a center of mass energy of √ s =7-13 TeV, the typical momentum transfer squared (Q 2 ) in the hard pp processes of photon or vector boson production accompanied by heavy flavor jets with large transverse momenta is above a few tenth of thousands of (GeV/c) 2 . At these scales, the contribution of the intrinsic charm component to the PDF features an enhancement at x ≥ 0.1, where the corresponding PDFs turn out to be larger (by more than an order of magnitude at x ∼ 0.3-0.4) than the sea (extrinsic) charm density distribution in the proton [16,21]. This can be seen in Fig.…”

“…Sensitivity studies of an IC signal in pp → γ +c(b)+X processes at LHC energies was recently done in [16]. Results indicate that the possible existence of an intrinsic heavy quark component in the proton can be inferred from the measurement of an enhancement (by factor of 2 or 3) of the number of events with a photon of p γ T > 150 GeV/c at high rapidity y γ in comparison with the relevant number of events expected in the absence of an IC contribution.…”

“…From the figure, one can also see that the high-Q 2 dependence of xc(x, Q 2 ) does not affect much the IC contribution to the PDF for x values above 0.1. The sensitivity studies performed with γ + c(b) + X processes in the context of the LHC demonstrated that, with the appropriate phase space selections on the final state photon and heavy flavor jets, one can select a large fraction of events with x c >0.1, and thus substantially intensify the intrinsic charm PDF contribution to charm hadroproduction, enough for being able to see a signal when compared to the extrinsic contribution alone [16]. In particular, it was shown that if, in at least one of the colliding protons, the momentum fraction of the c-quark x c is larger than the Feynman variable x γ F of the photon ,which, in turn, is larger than 0.1, i.e.…”

Characterization of the atmospheric muon flux in IceCube

“…The problem can therefore at the moment only be resolved experimentally [42]. One major open question currently under investigation [43] is whether nucleons contain "Intrinsic Charm" quarks, which might considerably increase charmed hadron production [44].…”

Intrinsic strange distributions in the nucleon from the light-cone models

“…Moreover, some analyses have been done to extract the probabilities of the light intrinsic quarks [6,34] using the existingd −ū data from the Fermilab E866 Drell-Yan experiment [35] and s +s data from the HERMES Collaboration measurement of charged kaon production in the semi-inclusive deep inelastic scattering (SIDIS) reaction [36]. There have also been some studies about the impact of the intrinsic charm quark on processes such as direct photon [37] and Z boson [38] production in association with a heavy quark or intrinsic bottom quark on heavy new physics [39] at the present hadron colliders such as LHC.…”