Highlights from LHCb

The recent highlights from LHCb in soft QCD and Heavy Ion physics are presented. This includes measurements from collisions of proton and lead 208 82 Pb 82+ ion beams with other beams as well as noble gas targets. An outlook on future analyses of 129 54 Xe 54+ collisions is presented.


Introduction
The LHCb detector is a unique apparatus for soft QCD and Heavy Ion physics. With the forward acceptance at high rapidity(y) 2 < y < 5; with excellent tracking; particle identification capabilities and a system for noble gas injection -the SMOG system -for fixed target collisions [1] with the LHC beam LHCb can do measurements no other experiment can do. Additional forward scintillators (HeRSCheL) in the region 5 < η < 9 can be used to select central exclusive events.

Fixed Target Physics
For fixed target physics in LHCb the SMOG system is used [1]. This system allows for the injection of noble gases in the accelerator vacuum. LHCb's acceptance then corresponds to a central rapidity range. LHCb has recorded the collisions of protons with Helium; Neon and Argon as well as collisions of lead 208 82 Pb 82+ ions with Argon.

Antiproton production in proton helium collisions at √ s NN = 110 GeV
Antiproton production in proton helium collisions is currently not well understood and is an important ingredient to the transport models of high energy cosmic rays [2,3]. The double differential cross section of antiproton production has been measured as a function of antiproton momentum and transverse momentum [4]; compared to EPOS LHC [5] and is presented in figure 1. This result is currently being updated with an improved determination of the luminosity for publication.   [5]. EPOS LHC predictions are systematically underestimating the data by a factor 1.5. Better agreement is found with EPOS 1.99 and HIJING.

First Observation of Ξ ++ cc
The first observation of the double charmed baryon Ξ ++ cc with the mass of m Ξ ++ cc = 3621.40 ± 0.72 ± 0.27 ± 0.140 MeV /c 2 is reported [6]. The first uncertainty is statistical; the second is systematic and the third originates from the limited knowledge of the Λ c mass. This measurement was performed using a data set corresponding to 2 fb −1 at √ s = 8 TeV and checked using 1fb −1 at √ s = 7 TeV of proton proton collisions.
This observation is in tension with a Ξ + cc state reported by the SELEX collaboration [7]. The difference to the mass reported by SELEX, m Ξ + cc = 3519 ± 2 MeV /c 2 is inconsistent with the presumption that those two states are separated by isospin only.

Open Charm Production at √ s = 5 TeV in Proton Proton Collisions
Measurements of the double differential cross section for D 0 , D + ,D + s and D + * production and the production ratios between 13 TeV and 5 TeV have been reported [9]. The data generally agree well with the FONLL, POWHEG+NNPDF3.0L and GMVFNS predictions for the ratios of cross-sections at √ s = 13 TeV and √ s = 5 TeV. Prompt D 0 production was measured in proton 208 82 Pb 82+ collisions. Double differential cross sections (y, p T ); forward backward ratios and nuclear modification factors have been measured [10]. The nuclear modification factor is shown in figure 2.  There is evidence for D + , D + s , Λ + c production as well as exclusive ρ 0 production in ultraperipheral collisions.  . Nuclear modification factor as a function of the rapidity in the centre of mass frame (y * ) for prompt (left) and non-prompt (right) J/ψ production at √ s NN = 5 TeV and at √ s NN = 8. 16 TeV compared to predictions from HELAC-Onia [11,12] using EPS09LO [15]; nCTEQ15 [16] and EPS09NLO [15] nuclear parton distribution functions and GCC and an energy loss model in the prompt case and to FONLL [17,18] using EPS09NLO [15] in the detached case.

Conclusions
The efforts to analyse ion collisions in LHCb start to bear fruits. Despite being geared for heavy flavour production in proton collisions and missing out on the first lead run of the LHC the LHCb collaboration is gaining momentum in heavy ion physics. Especially in the asymmetric collisions of protons with lead more interesting results are in preparation. The recently finished LHC run with xenon beams confirmed the LHCb capability to observe heavy flavour production in heavy ion collisions. Evidence for charm production shown in figure 4.