New insights into hadron production mechanism from $p_T$ spectra in $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$

We show that the experimental data of midrapidity $p_T$ spectra for $p$, $\mathrm{\Lambda }$, $\mathrm{\Xi }$, ${\mathrm{\Omega }}^{-}$, ${\mathrm{K}(892)}^{*0}$, and $\mathrm{\Xi }(1530{)}^{*0}$ in minimum-bias $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$ can be well fitted by the quark combination mechanism with the parametrized up(down) quark spectrum and strange quark spectrum at hadronization. The averaged transverse momentum $⟨p_T⟩$ and spectrum ratios such as $\mathrm{\Xi }/\mathrm{\Lambda }$ and $\mathrm{\Omega }/\varphi$ calculated from quark combination reproduce the data quite well. The available data of hadronic $p_T$ spectra released by ALICE collaboration in the first three high-multiplicity classes of $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$ are also well fitted. The extracted quark spectra at hadronization exhibit a dependence on the multiplicity class and also show a certain similarity to those obtained in $p\text{−}\mathrm{Pb}$ collisions at LHC and in relativistic heavy ion collisions. We make predictions for other hadrons, and propose two scaling behaviors among decuplet baryons and vector mesons as the effective probe of hadron production mechanism at such high collision energies.

Figure 1

Midrapidity $p_T$ spectra of identified hadrons in minimum-bias $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$. The solid lines are QCM results and symbols are experimental data [22, 23, 24, 25].

Figure 2

The ratios of average transverse momentum $⟨p_T⟩$ for experimental data to those for models or event generators in minimum-bias $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$ [22, 23, 24, 25].

Figure 3

$({\mathrm{\Omega }}^{-}+{\overline{\mathrm{\Omega }}}^{+})$ to $({\mathrm{\Xi }}^{-}+{\overline{\mathrm{\Xi }}}^{+})$ ratio as a function of $m_T-m_0$ in minimum-bias $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$. Solid squares are experimental data and solid circles are pythia Perugia 2011 simulation [49], which are taken from [23]. The line is our result.

Figure 4

${\mathrm{\Xi }}^{-}/\mathrm{\Lambda }$ ratio as a function of $p_T$ in minimum-bias $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$. Solid squares are experimental data from CMS collaboration [46] and thin lines are prediction of different pythia versions and/or tunes [53, 54, 55], which are taken from [46]. The thick line is our result.

Figure 5

$({\mathrm{\Omega }}^{-}+{\overline{\mathrm{\Omega }}}^{+})$ to $\varphi$ ratio as a function of $p_T$ in minimum-bias $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$. Solid squares are experimental data; dashed line is pythia Perugia 2011 simulation [49]; they are taken from [24]. The solid line is our result.

Figure 6

Midrapidity $p_T$ spectra of identified hadrons in first three high-multiplicity classes (I), (II), (III) in $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$. The solid lines are QCM results and symbols are experimental data. The data of $\mathrm{\Lambda }$, $\mathrm{\Xi }$ and ${\mathrm{\Omega }}^{-}$ are from [8] and those of proton and $\mathrm{K}(892{)}^{*0}$ are preliminary [57]. The data and our results in classes (II) and (III) are divided by factors 3 and $3^2$ for clarity, respectively.

Figure 7

$⟨p_T⟩$ of identified hadrons in first three high-multiplicity classes (I), (II), and (III) in $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$. Open symbols are experimental data [8, 58].

Figure 8

The $p_T$ spectra of $u$ and $s$ quarks in multiplicity class (I) and the ratio between them.

Figure 9

The scaled data for midrapidity $p_T$ spectra of ${\mathrm{\Omega }}^{-}$ and $\varphi$ in minimum-bias $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$ [8, 24] and those in different multiplicity classes in $p\text{−}\mathrm{Pb}$ collisions at $\sqrt{s_{NN}}=5.02\mathrm{TeV}$ [7, 26].

Figure 10

Midrapidity $p_T$ spectra of kaon and pion in minimum-bias $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$ and the ratio between them. Symbols are experimental data [22, 58] and results of other models and/or event generators are taken from [22, 51].