Compact Muon Solenoid
LHC, CERN
Visit us: CMS Public Website, CMS Physics ;
Contact us: CMS Publications Committee
| CMS-PAS-BPH-19-001 | ||
| Relative cross sections of the ${\rm B_c^+(2S)}$ and ${\rm B_c^{*+}(2S)}$ states with respect to the ${\rm B_c^+}$ state in proton-proton collisions at $\sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| May 2020 | ||
| Abstract: The ${\rm B_c^+(2S)}$ to ${\rm B_c^+}$ and ${\rm B_c^{*+}(2S)}$ to ${\rm B_c^+}$ cross section ratios, as well as the ${\rm B_c^{*+}(2S)}$ to ${\rm B_c^+(2S)}$ cross section ratio, are measured in proton-proton collisions at $\sqrt{s} = $ 13 TeV, using a data sample collected by the CMS experiment, corresponding to an integrated luminosity of 143 fb$^{-1}$. The three measurements are made in the ${\rm B_c^+}$ phase space window defined by transverse momentum $p_{\rm T} > $ 15 GeV and absolute rapidity $|y| < $ 2.4, with the excited ${\rm B_c^{(*)+}(2S)}$ states reconstructed in their ${\rm B_c^+} \pi^+ \pi^-$ decay. The ${\rm B_c^+(2S)}$ to ${\rm B_c^+}$, ${\rm B_c^{*+}(2S)}$ to ${\rm B_c^+}$, and ${\rm B_c^{*+}(2S)}$ to ${\rm B_c^+(2S)}$ cross section ratios, including the (unknown) ${\rm B_c^{(*)+}(2S) \to B_c^+}\pi^+\pi^-$ branching fractions, are (3.57 $\pm$ 0.69 (stat) $\pm$ 0.32 (syst) )%, (4.91 $\pm$ 0.69 (stat) $\pm$ 0.57 (syst) )%, and 1.39 $\pm$ 0.35 (stat) $\pm$ 0.09 (syst), respectively, where the first uncertainty is statistical and the second is systematic. None of these ratios shows a significant dependence on the $p_{\rm T}$ or $|y|$ of the ${\rm B_c^+}$. The shape of the invariant mass distribution of the dipions emitted in the ${\rm B_c^{(*)+}(2S) \to B_c^+}\pi^+\pi^-$ decays is also reported. | ||
|
Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, PRD 102 (2020) 092007. The superseded preliminary plots can be found here. |
||
| Figures | |
png pdf |
Figure 1:
Invariant mass distribution of the ${\mathrm{B_c}^{+} \to \mathrm{J}/\psi \pi^{+}}$ candidates, after applying all event selection criteria. The fitted contributions are shown by the stacked distributions, the solid line representing their sum. Taken from Ref. [1]. |
png pdf |
Figure 2:
Invariant mass distribution of the ${{{\mathrm{B_c}^{(*)+}} (\text{2S})} \to {\mathrm{B_c}^{+}} \pi^{+}\pi^{-}} $ candidates, the ${{{\mathrm{B_c}^{(*)+}} (\text{2S})}} $ being the lower-mass peak. The fitted contributions are shown by the stacked distributions, the solid line representing their sum. Taken from Ref. [1]. |
png pdf |
Figure 3:
The $R^{+}$, $R^{*+}$, and $R^{*+} / R^{+}$ cross section ratios as a function of the ${\mathrm{B_c}^{+}}$ ${p_{\mathrm {T}}}$ (left) and the ${\mathrm{B_c}^{+}}$ $ {|y|}$ (right). The markers are shown at the average ${\mathrm{B_c}^{+}}$ $ {p_{\mathrm {T}}} $ or $ {|y|}$ values of the events contributing to each bin. |
png pdf |
Figure 3-a:
The $R^{+}$, $R^{*+}$, and $R^{*+} / R^{+}$ cross section ratios as a function of the ${\mathrm{B_c}^{+}}$ ${p_{\mathrm {T}}}$ (left) and the ${\mathrm{B_c}^{+}}$ $ {|y|}$ (right). The markers are shown at the average ${\mathrm{B_c}^{+}}$ $ {p_{\mathrm {T}}} $ or $ {|y|}$ values of the events contributing to each bin. |
png pdf |
Figure 3-b:
The $R^{+}$, $R^{*+}$, and $R^{*+} / R^{+}$ cross section ratios as a function of the ${\mathrm{B_c}^{+}}$ ${p_{\mathrm {T}}}$ (left) and the ${\mathrm{B_c}^{+}}$ $ {|y|}$ (right). The markers are shown at the average ${\mathrm{B_c}^{+}}$ $ {p_{\mathrm {T}}} $ or $ {|y|}$ values of the events contributing to each bin. |
png pdf |
Figure 4:
Normalized invariant mass distribution of the dipions emitted in the ${{{\mathrm{B_c}^{(*)+}} (\text{2S})} \to {\mathrm{B_c}^{+}} \pi^{+}\pi^{-}} $ decays, $M(\pi^{+}\pi^{-})$. Both the statistical (inner tick marks) and the total (outer tick marks) uncertainties are represented. The histograms represent the two corresponding phase space distributions. |
| Tables | |
png pdf |
Table 1:
Ratios of the reconstruction efficiencies relevant for the determination of the $R^{+}$, $R^{*+}$, and $R^{*+} / R^{+}$ cross section ratios. The central values are followed by the several uncertainties mentioned in the text. |
png pdf |
Table 2:
Systematic uncertainties (in %) on the cross section ratios, corresponding to the sources described in the text. The total uncertainty is the sum in quadrature of the individual terms. |
| Summary |
|
The ${{\mathrm{B_c}^{+}} (\text{2S})}$ to ${\mathrm{B_c}^{+}}$ and ${{\mathrm{B_c}^{*+}} (\text{2S})}$ to ${\mathrm{B_c}^{+}}$ cross section ratios, as well as the ${{\mathrm{B_c}^{*+}} (\text{2S})}$ to ${{\mathrm{B_c}^{+}} (\text{2S})}$ cross section ratio, have been measured in proton-proton collisions at $\sqrt{s} = $ 13 TeV. The measurement was made on the basis of a data sample collected by the CMS experiment in the Run 2 of the LHC (2015-2018), corresponding to an integrated luminosity of 143 fb$^{-1}$. The ${{\mathrm{B_c}^{+}} (\text{2S})}$ to ${\mathrm{B_c}^{+}}$, ${{\mathrm{B_c}^{*+}} (\text{2S})}$ to ${\mathrm{B_c}^{+}}$, and ${{\mathrm{B_c}^{*+}} (\text{2S})}$ to ${{\mathrm{B_c}^{+}} (\text{2S})}$ cross section ratios, including the (unknown) ${{{\mathrm{B_c}^{(*)+}} (\text{2S})} \to {\mathrm{B_c}^{+}} \pi^{+}\pi^{-}} $ branching fractions, are $R^{*+} = $ 4.91 $\pm$ 0.69 (stat) $\pm$ 0.57 (syst) % $R^{*+} / R^{+} = $ 1.39 $\pm$ 0.35 (stat) $\pm$ 0.09 (syst) |
| References | ||||
| 1 | CMS Collaboration | Observation of two excited $ {\mathrm{B_c}^{(*)+}} $ states and measurement of the $ {\mathrm{B_c}^{(*)+}} (\text{2S}) $ mass in pp collisions at $ \sqrt{s} = $ 13 TeV | PRL 122 (2019) 132001 | CMS-BPH-18-007 1902.00571 |
| 2 | LHCb Collaboration | Observation of an excited $ {\mathrm{B_c}^{(*)+}} $ state | PRL 122 (2019) 232001 | 1904.00081 |
| 3 | E. J. Eichten and C. Quigg | Mesons with beauty and charm: New horizons in spectroscopy | PRD 99 (2019) 054025 | 1902.09735 |
| 4 | A. V. Berezhnoy, I. N. Belov, A. K. Likhoded, and A. V. Luchinsky | $ {\mathrm{B_c}^{(*)+}} $ excitations at LHC experiments | MPLA. 34 (2019) 1950331 | 1904.06732 |
| 5 | CMS Collaboration | The CMS trigger system | JINST 12 (2017) P01020 | CMS-TRG-12-001 1609.02366 |
| 6 | CMS Collaboration | Description and performance of track and primary-vertex reconstruction with the CMS tracker | JINST 9 (2014) P10009 | CMS-TRK-11-001 1405.6569 |
| 7 | CMS Collaboration | Performance of the CMS muon detector and muon reconstruction with proton-proton collisions at $ \sqrt{s}= $ 13 TeV | JINST 13 (2018) P06015 | CMS-MUO-16-001 1804.04528 |
| 8 | Particle Data Group, M. Tanabashi et al. | Review of Particle Physics | PRD 98 (2018) 030001 | |
| 9 | R. Fruhwirth, W. Waltenberger, and P. Vanlaer | Adaptive vertex fitting | JPG 34 (2007) N343 | |
| 10 | ARGUS Collaboration | Search for hadronic $ \mathrm{b} \to \mathrm{u} $ decays | PLB 241 (1990) 278 | |
| 11 | LHCb Collaboration | Measurement of the ratio of branching fractions $ \mathcal{B}({\mathrm{B_c}^{(*)+}} \to \mathrm{J}/\psi K^{+})/\mathcal{B}({\mathrm{B_c}^{(*)+}} \to \mathrm{J}/\psi\pi^{+}) $ | JHEP 09 (2016) 153 | 1607.06823 |
| 12 | C.-H. Chang, X.-Y. Wang, and X.-G. Wu | BCVEGPY2.2: a newly upgraded version for hadronic production of the meson bc and its excited states | CPC 197 (2015) 335 | 1507.05176 |
| 13 | T. Sjostrand et al. | An introduction to PYTHIA 8.2 | CPC 191 (2015) 159 | 1410.3012 |
| 14 | D. Lange | The EvtGen particle decay simulation package | NIMA 462 (2001) 152 | |
| 15 | N. Davidson, T. Przedzinski, and Z. Was | PHOTOS interface in C++: technical and physics documentation | CPC 199 (2016) 86 | 1011.0937 |
| 16 | GEANT4 Collaboration | GEANT4--a simulation toolkit | NIMA 506 (2003) 250 | |
| 17 | CMS Collaboration | CMS luminosity measurement for the 2015 data-taking period | CMS-PAS-LUM-15-001 | CMS-PAS-LUM-15-001 |
| 18 | CMS Collaboration | CMS luminosity measurements for the 2016 data taking period | CMS-PAS-LUM-17-001 | CMS-PAS-LUM-17-001 |
| 19 | CMS Collaboration | CMS luminosity measurement for the 2017 data-taking period at $ \sqrt{s} = $ 13 TeV | CMS-PAS-LUM-17-004 | CMS-PAS-LUM-17-004 |
| 20 | CMS Collaboration | CMS luminosity measurement for the 2018 data-taking period at $ \sqrt{s} = $ 13 TeV | CMS-PAS-LUM-18-002 | CMS-PAS-LUM-18-002 |
| 21 | M. J. Oreglia | A study of the reactions $\psi' \to \gamma\gamma \psi$ | PhD thesis, Stanford University, 1980 SLAC Report SLAC-R-236, see A | |
| 22 | A. Berezhnoy and A. Likhoded | The observation possibility of $ {\mathrm{B_c}^{(*)+}} $ excitations at LHC | PoS QFTHEP2013 (2013) 051 | 1307.5993 |
| 23 | M. Pivk and F. R. Le Diberder | SPlot: a statistical tool to unfold data distributions | NIMA 555 (2005) 356 | physics/0402083 |
|
|
Compact Muon Solenoid LHC, CERN |
|
|
|
|
|
|