Abstract (data abstract)

The first measurement of the multiplicity dependence of intra-jet properties of leading charged-particle jets in proton-proton (pp) collisions is reported. The mean charged-particle multiplicity and jet fragmentation distributions are measured in minimum-bias and high-multiplicity pp collisions at center-of-mass energy $\sqrt{s}$ = 13 TeV using the ALICE detector. Jets are reconstructed from charged particles produced in the midrapidity region ($|\eta| < 0.9$) using the sequential recombination anti-$k_{\rm T}$ algorithm with jet resolution parameters $R$ = 0.2, 0.3, and 0.4 for the transverse momentum ($p_{\rm T}$) interval 5$-$110 GeV/$c$. The high-multiplicity events are selected by the forward V0 scintillator detectors. The mean charged-particle multiplicity inside the leading jet cone rises monotonically with increasing jet $p_{\rm T}$ in qualitative agreement with previous measurements at lower energies. The distributions of jet fragmentation function variables $z^{\rm ch}$ and $\xi^{\rm ch}$ are measured for different jet-$p_{\rm T}$ intervals. Jet-$p_{\rm T}$ independent fragmentation of leading jets is observed for wider jets except at high- and low-$z^{\rm ch}$ values. The observed ``hump-backed plateau'' structure in the $\xi^{\rm ch}$ distribution indicates suppression of low-$p_{\rm T}$ particles. In high-multiplicity events, an enhancement of the fragmentation probability of low-$z^{\rm ch}$ particles accompanied by a suppression of high-$z^{\rm ch}$ particles is observed compared to minimum-bias events. This behavior becomes more prominent for low-$p_{\rm T}$ jets with larger jet radius. The results are compared with predictions of QCD-inspired event generators, PYTHIA 8 with Monash 2013 tune and EPOS LHC. It is found that PYTHIA 8 qualitatively reproduces the jet modification in high-multiplicity events except at high jet $p_{\rm T}$. These measurements provide important constraints to models of jet fragmentation.

Figure 1 (top)

Data from Figure 1 (top)

10.17182/hepdata.153919.v1/t1

Mean number of charged particles ($\langle N_{\mathrm{ch}} \rangle$) within leading charged-particle jets as a function of $p_{T}^{\mathrm{jet, ch}}$ for minimum-bias...
Figure 1 (bottom)

Data from Figure 1 (bottom)

10.17182/hepdata.153919.v1/t2

Mean number of charged particles ($\langle N_{\mathrm{ch}} \rangle$) within leading charged-particle jets as a function of $p_{T}^{\mathrm{jet, ch}}$ for high-multiplicity...
Figure 2

Data from Figure 2

10.17182/hepdata.153919.v1/t3

The ratio of $\langle N_{\mathrm{ch}} \rangle$ between high-multiplicity (HM) and minimum-bias (MB) events as a function of $p_{T}^{\mathrm{jet, ch}}$ for...
Figure 3 (top left)

Data from Figure 3 (top left)

10.17182/hepdata.153919.v1/t4

$z^{\mathrm{ch}}$ distributions in leading jets for different $p_{T}^{\mathrm{jet, ch}}$ intervals in minimum-bias (MB) pp collisions for jet resolution parameter ($R$)...
Figure 3 (top middle)

Data from Figure 3 (top middle)

10.17182/hepdata.153919.v1/t5

$z^{\mathrm{ch}}$ distributions in leading jets for different $p_{T}^{\mathrm{jet, ch}}$ intervals in minimum-bias (MB) pp collisions for jet resolution parameter ($R$)...
Figure 3 (top right)

Data from Figure 3 (top right)

10.17182/hepdata.153919.v1/t6

$z^{\mathrm{ch}}$ distributions in leading jets for different $p_{T}^{\mathrm{jet, ch}}$ intervals in minimum-bias (MB) pp collisions for jet resolution parameter ($R$)...
Figure 3 (bottom left)

Data from Figure 3 (bottom left)

10.17182/hepdata.153919.v1/t7

$z^{\mathrm{ch}}$ distributions in leading jets for different $p_{T}^{\mathrm{jet, ch}}$ intervals in high-multiplicity (HM) pp collisions for jet resolution parameter ($R$)...
Figure 3 (bottom middle)

Data from Figure 3 (bottom middle)

10.17182/hepdata.153919.v1/t8

$z^{\mathrm{ch}}$ distributions in leading jets for different $p_{T}^{\mathrm{jet, ch}}$ intervals in high-multiplicity (HM) pp collisions for jet resolution parameter ($R$)...
Figure 3 (bottom right)

Data from Figure 3 (bottom right)

10.17182/hepdata.153919.v1/t9

$z^{\mathrm{ch}}$ distributions in leading jets for different $p_{T}^{\mathrm{jet, ch}}$ intervals in high-multiplicity (HM) pp collisions for jet resolution parameter ($R$)...
Figure 5 (top)

Data from Figure 5 (top)

10.17182/hepdata.153919.v1/t10

The ratio of $z^{\mathrm{ch}}$ distributions for $10 < p_{\mathrm{T}}^{\mathrm{jet, ch}} < 20$ GeV/c between high-multiplicity (HM) and minimum-bias (MB) events...
Figure 5 (middle)

Data from Figure 5 (middle)

10.17182/hepdata.153919.v1/t11

The ratio of $z^{\mathrm{ch}}$ distributions for $30 < p_{\mathrm{T}}^{\mathrm{jet, ch}} < 40$ GeV/c between high-multiplicity (HM) and minimum-bias (MB) events...
Figure 5 (bottom)

Data from Figure 5 (bottom)

10.17182/hepdata.153919.v1/t12

The ratio of $z^{\mathrm{ch}}$ distributions for $60 < p_{\mathrm{T}}^{\mathrm{jet, ch}} < 80$ GeV/c between high-multiplicity (HM) and minimum-bias (MB) events...
Figure 7 (top left)

Data from Figure 7 (top left)

10.17182/hepdata.153919.v1/t13

$\xi^{\mathrm{ch}}$ distributions in leading jets for different $p_{T}^{\mathrm{jet, ch}}$ intervals in minimum-bias (MB) pp collisions for jet resolution parameter ($R$)...
Figure 7 (top middle)

Data from Figure 7 (top middle)

10.17182/hepdata.153919.v1/t14

$\xi^{\mathrm{ch}}$ distributions in leading jets for different $p_{T}^{\mathrm{jet, ch}}$ intervals in minimum-bias (MB) pp collisions for jet resolution parameter ($R$)...
Figure 7 (top right)

Data from Figure 7 (top right)

10.17182/hepdata.153919.v1/t15

$\xi^{\mathrm{ch}}$ distributions in leading jets for different $p_{T}^{\mathrm{jet, ch}}$ intervals in minimum-bias (MB) pp collisions for jet resolution parameter ($R$)...
Figure 7 (bottom left)

Data from Figure 7 (bottom left)

10.17182/hepdata.153919.v1/t16

$\xi^{\mathrm{ch}}$ distributions in leading jets for different $p_{T}^{\mathrm{jet, ch}}$ intervals in high-multiplicity (HM) pp collisions for jet resolution parameter ($R$)...
Figure 7 (bottom middle)

Data from Figure 7 (bottom middle)

10.17182/hepdata.153919.v1/t17

$\xi^{\mathrm{ch}}$ distributions in leading jets for different $p_{T}^{\mathrm{jet, ch}}$ intervals in high-multiplicity (HM) pp collisions for jet resolution parameter ($R$)...
Figure 7 (bottom right)

Data from Figure 7 (bottom right)

10.17182/hepdata.153919.v1/t18

$\xi^{\mathrm{ch}}$ distributions in leading jets for different $p_{T}^{\mathrm{jet, ch}}$ intervals in high-multiplicity (HM) pp collisions for jet resolution parameter ($R$)...
Figure 9 (top)

Data from Figure 9 (top)

10.17182/hepdata.153919.v1/t19

The ratio of $\xi^{\mathrm{ch}}$ distributions for $10 < p_{\mathrm{T}}^{\mathrm{jet, ch}} < 20$ GeV/c between high-multiplicity (HM) and minimum-bias (MB) events...
Figure 9 (middle)

Data from Figure 9 (middle)

10.17182/hepdata.153919.v1/t20

The ratio of $\xi^{\mathrm{ch}}$ distributions for $30 < p_{\mathrm{T}}^{\mathrm{jet, ch}} < 40$ GeV/c between high-multiplicity (HM) and minimum-bias (MB) events...
Figure 9 (bottom)

Data from Figure 9 (bottom)

10.17182/hepdata.153919.v1/t21

The ratio of $\xi^{\mathrm{ch}}$ distributions for $60 < p_{\mathrm{T}}^{\mathrm{jet, ch}} < 80$ GeV/c between high-multiplicity (HM) and minimum-bias (MB) events...

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