# Study of $D_J$ meson decays to $D^+\pi^-$, $D^0 \pi^+$ and $D^{*+}\pi^-$ final states in $pp$ collisions

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## Abstract

A study of $D^+\pi^-$, $D^0 \pi^+$ and $D^{*+}\pi^-$ final states is performed using pp collision data, corresponding to an integrated luminosity of 1.0 $fb^{-1}$, collected at a centre-of-mass energy of 7 TeV with the LHCb detector. The $D_1(2420)^0$ resonance is observed in the $D^{*+}\pi^-$ final state and the $D^*_2(2460)$ resonance is observed in the $D^+\pi^-$, $D^0 \pi^+$ and $D^{*+}\pi^-$ final states. For both resonances, their properties and spin-parity assignments are obtained. In addition, two natural parity and two unnatural parity resonances are observed in the mass region between 2500 and 2800 MeV. Further structures in the region around 3000 MeV are observed in all the $D^{*+}\pi^-$, $D^+\pi^-$ and $D^0 \pi^+$ final states.

## Figures and captions

 Modified Godfrey-Isgur mass predictions \cite{Godfrey:1985xj}. The figure shows the $c\bar{u}$ spectrum in which the masses have been scaled such that the ground state coincides with the $D^0$ mass. The $2^-$ states, not shown in the original publication, have been inserted following the splitting structure of the 1P states. fig1.pdf [13 KiB] HiDef png [135 KiB] Thumbnail [44 KiB] *.C file Invariant mass distribution for (a) $D ^+ \rightarrow K^-\pi^+\pi^+$, (b) $D ^0 \rightarrow K^-\pi^+$, and (c) $D ^{*+} \rightarrow D ^0 \pi ^+$ decays. The solid lines are the results from the fits described in the text. The vertical dashed lines indicate the signal regions. fig2.pdf [31 KiB] HiDef png [409 KiB] Thumbnail [163 KiB] *.C file Invariant mass distribution for (a) $D ^+ \pi ^-$, (b) $D ^0 \pi ^+$ and (c) $D ^{*+} \pi ^-$ candidates (points). The full line histograms (in red) show the wrong-sign mass spectra for (a) $D ^+ \pi ^+$, (b) $D ^0 \pi ^-$ and (c) $D ^{*+} \pi ^+$ normalized to the same yield at high $D^{(*)}\pi$ masses. fig3.pdf [39 KiB] HiDef png [428 KiB] Thumbnail [154 KiB] *.C file Fit to the $D ^{*+} \pi ^-$ mass spectrum, {\it enhanced unnatural parity sample}, as defined in Table ???. The dashed (blue) line shows the fitted background, the dotted (red) line the $D_1(2420)^0$ contribution. The inset displays the $D ^{*+} \pi ^-$ mass spectrum after subtracting the fitted background. The full line curves (blue) show the contributions from $D_{J}(2580)^0$ , $D_{J}(2740)^0$ , and $D_{J}(3000)^0$ states. The top window displays the pull distribution where the horizontal lines indicate $\pm 3 \sigma$. The pull is defined as $(N_{\rm data} - N_{\rm fit})/\sqrt{N_{\rm data}}$. fig4.pdf [71 KiB] HiDef png [319 KiB] Thumbnail [89 KiB] *.C file Fit to the {\it natural parity sample} $D ^{*+} \pi ^-$ mass spectrum. The dashed (blue) line shows the fitted background, the dotted lines the $D_1(2420)^0$ (red) and ${D}^*_2(2460)^0$ (blue) contributions. The inset displays the $D ^{*+} \pi ^-$ mass spectrum after subtracting the fitted background. The full line curves (red) show the contributions from $D_{J}(2580)^0$ , $D_{J}(2740)^0$ , and $D_{J}(3000)^0$ . The dotted (blue) lines display the $D^*_{J}(2650)^0$ and $D^*_{J}(2760)^0$ contributions. The top window shows the pull distribution where the horizontal lines indicate $\pm 3 \sigma$. fig5.pdf [76 KiB] HiDef png [337 KiB] Thumbnail [93 KiB] *.C file Fit to the {\it unnatural parity sample} $D ^{*+} \pi ^-$ mass spectrum. The dashed (blue) line shows the fitted background, the dotted lines the $D_1(2420)^0$ (red) and ${D}^*_2(2460)^0$ (blue) contributions. The inset displays the $D ^{*+} \pi ^-$ mass spectrum after subtracting the fitted background. The full line curves (red) show the contributions from $D_{J}(2580)^0$ , $D_{J}(2740)^0$ , and $D_{J}(3000)^0$ states. The dotted (blue) lines display the $D^*_{J}(2650)^0$ and $D^*_{J}(2760)^0$ contributions. The top window shows the pull distribution where the horizontal lines indicate $\pm 3 \sigma$. fig6.pdf [74 KiB] HiDef png [334 KiB] Thumbnail [93 KiB] *.C file Fit to the total $D ^{*+} \pi ^-$ sample. The dashed (blue) line shows the fitted background, the dotted lines the $D_1(2420)^0$ (red) and ${D}^*_2(2460)^0$ (blue) contributions. The inset displays the $D ^{*+} \pi ^-$ mass spectrum after subtracting the fitted background. The full line curves (red) show the contributions from $D_{J}(2580)^0$ , $D_{J}(2740)^0$ , and $D_{J}(3000)^0$ states. The dotted (blue) lines display the $D^*_{J}(2650)^0$ and $D^*_{J}(2760)^0$ contributions. The top window shows the pull distribution where the horizontal lines indicate $\pm 3 \sigma$. fig7.pdf [72 KiB] HiDef png [332 KiB] Thumbnail [92 KiB] *.C file Distributions of (a) $D_1(2420)^0$ and (b) ${D}^*_2(2460)^0$ candidates as functions of the helicity angle $\cos\theta_{\rm H}$ . The distributions are fitted with unnatural and natural parity functions, respectively. fig8.pdf [17 KiB] HiDef png [126 KiB] Thumbnail [48 KiB] *.C file Distributions of (a) $D^*_{J}(2650)^0$ and (b) $D^*_{J}(2760)^0$ candidates as functions of the helicity angle $\cos\theta_{\rm H}$ . The distributions are fitted with natural parity (black continuous), unnatural parity (red, dashed) and $J^P=0^-$ (blue, dotted) functions. fig9.pdf [20 KiB] HiDef png [203 KiB] Thumbnail [74 KiB] *.C file Distributions of (a) $D_{J}(2580)^0$ , (b) $D_{J}(2740)^0$ and (c) $D_{J}(3000)^0$ candidates as functions of the helicity angle $\cos\theta_{\rm H}$ . The distributions are fitted with natural parity (black continuous) and unnatural parity (red, dashed) functions. In (a) the $J^P=0^-$ (blue, dotted) hypothesis is also tested. fig10.pdf [22 KiB] HiDef png [189 KiB] Thumbnail [56 KiB] *.C file Fit to the $D ^+ \pi ^-$ mass spectrum. The filled histogram (in red) shows the estimated cross-feeds from the high mass $D ^* \pi$ resonances. The dashed (blue) line displays the fitted background. The dotted (blue) line shows the ${D}^*_2(2460)^0$ contribution. The inset displays the mass spectrum after the fitted background subtraction. The full (blue) curves show the $D^*_{J}(2760)^0$ and $D^*_{J}(3000)^0$ contributions. The top window displays the pull distribution where the horizontal lines indicate $\pm 3 \sigma$. fig11.pdf [76 KiB] HiDef png [313 KiB] Thumbnail [90 KiB] *.C file Fit to the $D ^0 \pi ^+$ mass spectrum. The filled histogram (in red) shows the estimated cross-feeds from the high mass $D ^* \pi$ resonances. The dashed (blue) line displays the fitted background. The dotted (blue) line shows the ${D}^*_2(2460)^+$ contribution. The inset displays the mass spectrum after the fitted background subtraction. The full (blue) curves show the $D^*_{J}(2760)^+$ and $D^*_{J}(3000)^+$ contributions. The top window displays the pull distribution where the horizontal lines indicate $\pm 3 \sigma$. fig12.pdf [76 KiB] HiDef png [295 KiB] Thumbnail [87 KiB] *.C file Animated gif made out of all figures. PAPER-2013-026.gif Thumbnail

## Tables and captions

 Breit-Wigner parameters describing the cross-feed from $D_1(2420)$ and $D^*_2(2460)$ in the $D ^+ \pi ^-$ and $D ^0 \pi ^+$ final states. Table_1.pdf [37 KiB] HiDef png [52 KiB] Thumbnail [8 KiB] tex code Definition of the categories selected by different ranges of $\cos\theta_{\rm H}$ , and fraction of the total natural parity contribution. Table_2.pdf [49 KiB] HiDef png [44 KiB] Thumbnail [6 KiB] tex code Mass intervals, number of bins, yields, and $\chi^2/{\rm ndf}$ in the fits to the different mass spectra. Table_3.pdf [58 KiB] HiDef png [78 KiB] Thumbnail [11 KiB] tex code

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