# Search for the doubly charmed baryon $\Xi_{cc}^+$

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## Abstract

A search for the doubly charmed baryon Xi_cc^+ in the decay mode Xi_cc^+ -> Lambda_c^+ K^- pi^+ is performed with a data sample, corresponding to an integrated luminosity of 0.65/fb, of pp collisions recorded at a centre-of-mass energy of 7 TeV. No significant signal is found in the mass range 3300-3800 MeV/c^2. Upper limits at the 95% confidence level on the ratio of the Xi_cc^+ production cross-section times branching fraction to that of the Lambda_c^+, R, are given as a function of the Xi_cc^+ mass and lifetime. The largest upper limits range from R < 1.5 x 10^-2 for a lifetime of 100 fs to R < 3.9 x 10^-4 for a lifetime of 400 fs.

## Figures and captions

 Invariant mass spectrum of $\Lambda _ c ^+ \rightarrow p K ^- \pi ^+$ candidates for 5$\%$ of the data, with events chosen at random during preselection (due to bandwidth limits for the normalisation mode). The dashed line shows the fitted background contribution, and the solid line the sum of $\Lambda _ c ^+$ signal and background. pub-Lc-bw.pdf [25 KiB] HiDef png [151 KiB] Thumbnail [152 KiB] *.C file The distribution of the invariant mass difference $\delta m$, defined in Eq. 3, for simulated $\Xi_{ c c }^+$ events with a $\Xi_{ c c }^+$ mass of 3500 ${\mathrm{ Me V /}c^2}$ . The solid line shows the fitted signal shape. In order to increase the available statistics, the trigger and ANN requirements are not applied in this plot. pub-Xi[..].pdf [22 KiB] HiDef png [149 KiB] Thumbnail [142 KiB] *.C file Spectrum of $\delta m$ requiring $2273 < m([ p K ^- \pi ^+ ]_{\Lambda _ c }) < 2303$ ${\mathrm{ Me V /}c^2}$ . Both plots show the same data sample, but with different $\delta m$ ranges and binnings. The wide signal region is shown in the right plot and indicated by the dotted vertical lines in the left plot. pub-sp[..].pdf [17 KiB] HiDef png [146 KiB] Thumbnail [157 KiB] *.C file pub-sp[..].pdf [18 KiB] HiDef png [171 KiB] Thumbnail [180 KiB] *.C file Measured signal yields as a function of $\delta m$. The upper two plots show the estimated signal yield as a dark line and the $\pm 1\sigma$ statistical error bands as light grey lines for (upper left) the baseline method and (upper right) the cross-check method. The central values of the two methods are compared in the lower plot and found to agree well. pub-yi[..].pdf [23 KiB] HiDef png [480 KiB] Thumbnail [296 KiB] *.C file pub-yi[..].pdf [23 KiB] HiDef png [419 KiB] Thumbnail [268 KiB] *.C file pub-yi[..].pdf [20 KiB] HiDef png [274 KiB] Thumbnail [228 KiB] *.C file Upper limits on $R$ at the 95% CL as a function of $\delta m$, for five $\Xi_{ c c }^+$ lifetime hypotheses. pub-li[..].pdf [29 KiB] HiDef png [351 KiB] Thumbnail [302 KiB] *.C file Mass difference spectrum requiring $2273 < m([ p K ^- \pi ^+ ]_{\Lambda _ c }) < 2303$ ${\mathrm{ Me V /}c^2}$ . Candidates are also required to be consistent with (left) an intermediate $\Sigma_{ c }(2455)^{++}$, (right) an intermediate $\Sigma_{ c }(2520)^{++}$. pub-sp[..].pdf [14 KiB] HiDef png [110 KiB] Thumbnail [122 KiB] *.C file pub-sp[..].pdf [14 KiB] HiDef png [115 KiB] Thumbnail [127 KiB] *.C file Animated gif made out of all figures. PAPER-2013-049.gif Thumbnail

## Tables and captions

 Systematic uncertainties on the single-event sensitivity $\alpha$. Table_1.pdf [24 KiB] HiDef png [156 KiB] Thumbnail [65 KiB] tex code Single-event sensitivity $\alpha$ for different lifetime hypotheses $\tau$, assuming $m(\Xi_{ c c }^+ )=3500$ ${\mathrm{ Me V /}c^2}$ . The uncertainties quoted include statistical and systematic effects, and are correlated between different lifetime hypotheses. Table_2.pdf [40 KiB] HiDef png [150 KiB] Thumbnail [56 KiB] tex code Variation in single-event sensitivity for different mass hypotheses $m(\Xi_{ c c }^+ )$, assuming $\tau=333$ $\rm fs$ . The uncertainties quoted include statistical and systematic effects, and are correlated between different mass hypotheses. The variation is shown separately for all effects other than the efficiency of the $\delta m$ window ($\alpha_u$), for the correction due to the mass-dependent resolution, and for the combination ($\alpha$). Table_3.pdf [51 KiB] HiDef png [54 KiB] Thumbnail [27 KiB] tex code Expected value of the signal yield $N_{\text{sig}}$ for different values of $R$ and lifetime hypotheses, assuming $m(\Xi_{ c c }^+ )=3500$ ${\mathrm{ Me V /}c^2}$ . The uncertainties quoted are due to the systematic uncertainty on $\alpha$. Table_4.pdf [41 KiB] HiDef png [85 KiB] Thumbnail [42 KiB] tex code Largest values of the upper limits (UL) on $R$ at the 95% CL in blocks of $\delta m$ for a range of lifetime hypotheses, given in units of $10^{-3}$. The largest values across the entire 500 ${\mathrm{ Me V /}c^2}$ range are also shown. Table_5.pdf [38 KiB] HiDef png [144 KiB] Thumbnail [71 KiB] tex code

## Supplementary Material [file]

 Colour versions of figures in LHCb-PAPER-2013-049. Fig1.pdf [25 KiB] HiDef png [175 KiB] Thumbnail [150 KiB] *C file Fig2.pdf [23 KiB] HiDef png [174 KiB] Thumbnail [146 KiB] *C file Fig3a.pdf [17 KiB] HiDef png [155 KiB] Thumbnail [154 KiB] *C file Fig4a.pdf [23 KiB] HiDef png [560 KiB] Thumbnail [289 KiB] *C file Fig4b.pdf [23 KiB] HiDef png [490 KiB] Thumbnail [261 KiB] *C file Fig4c.pdf [20 KiB] HiDef png [402 KiB] Thumbnail [204 KiB] *C file Fig5.pdf [29 KiB] HiDef png [467 KiB] Thumbnail [286 KiB] *C file

Created on 19 October 2019.