# Inclusive low mass Drell-Yan production in the forward region at $\sqrt{s}$ = 7 TeV

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## Abstract

This note presents the measurement of the Drell-Yan cross-section in dimuon final states for muons within pseudorapidities of 2 to 4.5, in the mass range $5<M_{\mu\mu}<120$ ${\mathrm{\,Ge V\!/}c^2}$ . The muons are required to have a momentum larger than $10$ ${\mathrm{\,Ge V\!/}c}$ and a transverse momentum larger that $3$ ${\mathrm{\,Ge V\!/}c}$ . For masses above $40$ ${\mathrm{\,Ge V\!/}c^2}$ the transverse momentum needs to be larger than $15$ ${\mathrm{\,Ge V\!/}c}$ . The cross section is measured differentially, in mass, and in rapidity of the virtual photon ($\gamma^\star$) in two distinct mass regions. The analysis uses the full dataset collected by the LHCb experiment during 2010 with an integrated luminosity of $37$ $\,pb^{-1}$ .

## Figures and captions

 The top plots show the dimuon invariant mass for the $Z\rightarrow\mu\mu$ (left) and the $\Upsilon$ (right) samples. The lower plots show the dimuon invariant mass for ${ J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ (left) and the ${ J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}K$ (right) samples used to determine the muon identification and tracking efficiencies. A Crystal Ball function for the signal and an exponential for the background are fitted to all four distributions. ZMass.pdf [15 KiB] HiDef png [165 KiB] Thumbnail [58 KiB] *.C file Upsilo[..].pdf [17 KiB] HiDef png [194 KiB] Thumbnail [66 KiB] *.C file JpsiMa[..].pdf [16 KiB] HiDef png [195 KiB] Thumbnail [70 KiB] *.C file JpsiMa[..].pdf [16 KiB] HiDef png [182 KiB] Thumbnail [68 KiB] *.C file Misidentification probability for muons due to decay in flight as a function of the longitudinal momentum together with the fit for the misidentification probability. MuonMi[..].pdf [14 KiB] HiDef png [146 KiB] Thumbnail [62 KiB] *.C file Comparison of data and simulation of the distribution of the minimum isolation for muons from $\Upsilon\rightarrow\mu\mu$ (left) and $Z\rightarrow\mu\mu$ (right) decays. MCdata[..].pdf [16 KiB] HiDef png [154 KiB] Thumbnail [45 KiB] *.C file Comparison of data and simulation of the distribution of the minimum isolation for muons from the two heavy flavour templates (left) and the two templates for MisID (right). HF_tem[..].pdf [15 KiB] HiDef png [282 KiB] Thumbnail [63 KiB] *.C file ID_tem[..].pdf [15 KiB] HiDef png [269 KiB] Thumbnail [65 KiB] *.C file Template fit to the minimum muon isolation distribution for nine mass bins. The data (points) are compared to the fitted contributions from $\gamma^\star\rightarrow\mu\mu$ (blue) and backgrounds from heavy flavour decays (red) and muon misidentification(green). Mass.pdf [182 KiB] HiDef png [1 MiB] Thumbnail [138 KiB] *.C file Template fit to the minimum muon isolation distribution for five rapidity bins and $10.540$ ${\mathrm{\,Ge V\!/}c}$ have a cut of $p^\mu_\mathrm{T}>15$ ${\mathrm{\,Ge V\!/}c}$ for the data and the predictions. The lower plot shows the ratio of the predictions or the uncertainties to the data. CSDYM1.pdf [17 KiB] HiDef png [344 KiB] Thumbnail [67 KiB] *.C file Differential cross-section for $\gamma^\star\rightarrow\mu\mu$ as a function of $M_{\mu\mu}$. The dark shaded (orange) bands correspond to the statistical uncertainties, the light shaded (yellow) band to the statistical and systematic uncertainties added in quadrature. Superimposed are NLO predictions from FEWZ with the PDF sets from MSTW08, NNPDF and CTEQ; they are displaced horizontally for presentation. The NLO uncertainties correspond to the PDF uncertainties evaluated at the 68% confidence level. The two bins with $M_{\mu\mu}>40$ ${\mathrm{\,Ge V\!/}c}$ have a cut of $p^\mu_\mathrm{T}>15$ ${\mathrm{\,Ge V\!/}c}$ for the data and the predictions. CSDYM2.pdf [15 KiB] HiDef png [270 KiB] Thumbnail [53 KiB] *.C file Differential cross-section for $\gamma^\star\rightarrow\mu\mu$ as a function of $y$ for two different mass regions of the dimuon system. The dark shaded (orange) bands correspond to the statistical uncertainties, the light shaded (yellow) band to the statistical and systematic uncertainties added in quadrature. The shaded vertical band corresponds to the mass region of the $\Upsilon$ which is not included in the measurement. Superimposed are NLO predictions from FEWZ with the PDF sets from MSTW08, NNPDF and CTEQ; they are displaced horizontally for presentation. The NLO uncertainties correspond to the PDF uncertainties evaluated at the 68% confidence level. CSDYE2.pdf [15 KiB] HiDef png [275 KiB] Thumbnail [62 KiB] *.C file CSDYE3.pdf [15 KiB] HiDef png [250 KiB] Thumbnail [60 KiB] *.C file Animated gif made out of all figures. CONF-2012-013.gif Thumbnail

## Tables and captions

 Cross section in bins of the invariant mass of the muon pair. The two bins with $M_{\mu\mu}>40$ ${\mathrm{\,Ge V\!/}c}$ have a cut of $p^\mu_\mathrm{T}>15$ ${\mathrm{\,Ge V\!/}c}$ . Table_1.pdf [37 KiB] HiDef png [76 KiB] Thumbnail [13 KiB] tex code Cross section in bins of the rapidity of the dimuons for two different mass regions. Table_2.pdf [37 KiB] HiDef png [76 KiB] Thumbnail [13 KiB] tex code

Created on 20 April 2019.Citation count from INSPIRE on 20 April 2019.