System size dependence of associated yields in hadron-triggered jets

The STAR collaboration Abelev, B.I. ; Aggarwal, M.M. ; Ahammed, Z. ; et al.
Phys.Lett.B 683 (2010) 123-128, 2010.
Inspire Record 817691 DOI 10.17182/hepdata.102091

We present results on the system size dependence of high transverse momentum di-hadron correlations at $\sqrt{s_{NN}}$ = 200 GeV as measured by STAR at RHIC. Measurements in d+Au, Cu+Cu and Au+Au collisions reveal similar jet-like correlation yields at small angular separation ($\Delta\phi\sim0$, $\Delta\eta\sim0$) for all systems and centralities. Previous measurements have shown that the away-side yield is suppressed in heavy-ion collisions. We present measurements of the away-side suppression as a function of transverse momentum and centrality in Cu+Cu and Au+Au collisions. The suppression is found to be similar in Cu+Cu and Au+Au collisions at a similar number of participants. The results are compared to theoretical calculations based on the parton quenching model and the modified fragmentation model. The observed differences between data and theory indicate that the correlated yields presented here will provide important constraints on medium density profile and energy loss model parameters.

31 data tables

Di-hadron correlations in $\Delta\phi$ for small $|\Delta\eta|$ ($|\Delta\eta|<0.7$) and large ($0.7<|\Delta\eta|<1.7$), scaled to match small $|\Delta\eta|$ at large $\Delta\phi$.

Subtracted distributions for di-hadron correlations in $\Delta\phi$ for small $|\Delta\eta|$ ($|\Delta\eta|<0.7$) minus large ($0.7<|\Delta\eta|<1.7$), scaled to match small $|\Delta\eta|$ at large $\Delta\phi$.

Subtracted distributions for di-hadron correlations in $\Delta\eta$.

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Measurement of inclusive charged-particle jet production in Au + Au collisions at $\sqrt{s_{NN}}=$200 GeV

The STAR collaboration Adam, J. ; Adamczyk, L. ; Adams, J.R. ; et al.
Phys.Rev.C 102 (2020) 054913, 2020.
Inspire Record 1798665 DOI 10.17182/hepdata.95120

The STAR Collaboration at the Relativistic Heavy Ion Collider reports the first measurement of inclusive jet production in peripheral and central Au+Au collisions at $\sqrt{s_{NN}}$~=~200 GeV. Jets are reconstructed with the anti-k$_{T}$ algorithm using charged tracks with pseudo--rapidity $|\eta|<1.0$ and transverse momentum $0.2<p_{T}<30$ GeV/$c$, with jet resolution parameter $R$~=~0.2, 0.3, and 0.4. The large background yield uncorrelated with the jet signal is observed to be dominated by statistical phase space, consistent with a previous coincidence measurement. This background is suppressed by requiring a high transverse-momentum (high-$p_T$) leading hadron in accepted jet candidates. The bias imposed by this requirement is assessed, and the $p_T$-region in which the bias is small is identified. Inclusive charged-particle jet distributions are reported in peripheral and central Au+Au collisions for $5<p_{T,jet}^{ch}<25$ GeV/$c$ and $5<p_{T,jet}^{ch}<30$ GeV/$c$, respectively. The charged-particle jet inclusive yield is suppressed for central Au+Au collisions, compared to both the peripheral Au+Au yield from this measurement and to the $pp$ yield calculated using the PYTHIA event generator. The magnitude of the suppression is consistent with that of inclusive hadron production at high $p_T$, and that of semi-inclusive recoil jet yield when expressed in terms of energy loss due to medium-induced energy transport. Comparison of inclusive charged-particle jet yields for different values of $R$ exhibits no significant evidence for medium-induced broadening of the transverse jet profile for $R<0.4$ in central Au+Au collisions. The measured distributions are consistent with theoretical model calculations that incorporate jet quenching.

12 data tables

Corrected inclusive charged-particle jet distributions in Au+Au collisions at 200 GeV for R=0.2, 0.3, and 0.4 in central (0-10%) Au+Au collisions for pTlead,min = 5 GeV/c. The first uncertainty is statistical (symmetric), followed by shape uncertainty (asymmetric) and correlated uncertainty (asymmetric).

Corrected inclusive charged-particle jet distributions in Au+Au collisions at 200 GeV for R=0.2, 0.3, and 0.4 in peripheral (60-80%) Au+Au collisions for pTlead,min = 5 GeV/c. The first uncertainty is statistical (symmetric), followed by shape uncertainty (asymmetric) and correlated uncertainty (asymmetric).

Corrected inclusive charged-particle jet distributions in Au+Au collisions at 200 GeV for R=0.2, 0.3, and 0.4 in central (0-10%) Au+Au collisions for pTlead,min = 7 GeV/c. The first uncertainty is statistical (symmetric), followed by shape uncertainty (asymmetric) and correlated uncertainty (asymmetric).

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Version 2
Global polarization of $\Lambda$ hyperons in Au+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV

The STAR collaboration Adam, Jaroslav ; Adams, Joseph ; Agakishiev, Geydar ; et al.
Phys.Rev.C 98 (2018) 014910, 2018.
Inspire Record 1672785 DOI 10.17182/hepdata.99054

Global polarization of $\Lambda$ hyperons has been measured to be of the order of a few tenths of a percent in Au+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV, with no significant difference between $\Lambda$ and $\bar{\Lambda}$. These new results reveal the collision energy dependence of the global polarization together with the results previously observed at $\sqrt{s_{_{NN}}}$ = 7.7 -- 62.4 GeV and indicate noticeable vorticity of the medium created in non-central heavy-ion collisions at the highest RHIC collision energy. The signal is in rough quantitative agreement with the theoretical predictions from a hydrodynamic model and from the AMPT (A Multi-Phase Transport) model. The polarization is larger in more peripheral collisions, and depends weakly on the hyperon's transverse momentum and pseudorapidity $\eta^H$ within $|\eta^H|<1$. An indication of the polarization dependence on the event-by-event charge asymmetry is observed at the $2\sigma$ level, suggesting a possible contribution to the polarization from the axial current induced by the initial magnetic field.

10 data tables

$\Lambda$ ($\bar\Lambda$) polarization as a function of the collision centrality in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV. Open boxes and vertical lines show systematic and statistical uncertainties. The data points for Λ are slightly shifted for visibility.

Global polarization of $\Lambda$ and $\bar{\Lambda}$ as a function of the collision energy $\sqrt{s_{_{NN}}}$ for 20-50% centrality Au+Au collisions. Thin lines show calculations from a 3+1D cascade + viscous hydrodynamic model (UrQMD+vHLLE) and bold lines show the AMPT model calculations. In the case of each model, primary $\Lambda$ with and without the feed-down effect are indicated by dashed and solid lines, respectively. Open boxes and vertical lines show systematic and statistical uncertainties, respectively. Note that the data points at 200 GeV and for $\bar{\Lambda}$ are slightly horizontally shifted for visibility.

Polarization of $\Lambda$ and $\bar\Lambda$ as a function of $p_{T}$ for the $20\%–60\%$ centrality bin in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV. Open boxes and vertical lines show systematic and statistical uncertainties, respectively. Hydrodynamic model calculations for Λ with two different initial conditions (IC) are compared. Note that the data points for Λ are slightly shifted for visibility.

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Observation of excess J/$\psi$ yield at very low transverse momenta in Au+Au collisions at $\sqrt{s_{\rm{NN}}} =$ 200 GeV and U+U collisions at $\sqrt{s_{\rm{NN}}} =$ 193 GeV

The STAR collaboration Adam, J. ; Adamczyk, L. ; Adams, J.R. ; et al.
Phys.Rev.Lett. 123 (2019) 132302, 2019.
Inspire Record 1731573 DOI 10.17182/hepdata.91138

We report on the first measurements of J/$\psi$ production at very low transverse momentum ($p_{T} <$ 0.2 GeV/c) in hadronic Au+Au collisions at $\sqrt{s_{\rm{NN}}} =$ 200 GeV and U+U collisions at $\sqrt{s_{\rm{NN}}} =$ 193 GeV. Remarkably, the inferred nuclear modification factor of J/$\psi$ at mid-rapidity in Au+Au (U+U) collisions reaches about 24 (52) for $p_{T} <$ 0.05 GeV/c in the 60-80$\%$ collision centrality class. This noteworthy enhancement cannot be explained by hadronic production accompanied by cold and hot medium effects. In addition, the $dN/dt$ distribution of J/$\psi$ for the very low $p_{T}$ range is presented for the first time. The distribution is consistent with that expected from the Au nucleus and shows a hint of interference. Comparison of the measurements to theoretical calculations of coherent production shows that the excess yield can be described reasonably well and reveals a partial disruption of coherent production in semi-central collisions, perhaps due to the violent hadronic interactions. Incorporating theoretical calculations, the results strongly suggest that the dramatic enhancement of J/$\psi$ yield observed at extremely low $p_{T}$ originates from coherent photon-nucleus interactions. In particular, coherently produced J/$\psi$'s in violent hadronic collisions may provide a novel probe of the quark-gluon-plasma.

8 data tables

'$J/\Psi$ invariant yields for Au+Au collisions 200 GeV as a function of $p_T$'

'$J/\Psi$ invariant yields for U+U collisions 193 GeV as a function of $p_T$'

'$J/\Psi$ $R_{AA}$ for Au+Au collisions 200 GeV as a function of $p_T$'

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Growth of Long Range Forward-Backward Multiplicity Correlations with Centrality in Au+Au Collisions at s(NN)**(1/2) = 200-GeV

The STAR collaboration Abelev, B.I. ; Aggarwal, M.M. ; Ahammed, Z. ; et al.
Phys.Rev.Lett. 103 (2009) 172301, 2009.
Inspire Record 819318 DOI 10.17182/hepdata.102090

Forward-backward multiplicity correlation strengths have been measured for the first time with the STAR detector for Au+Au and $\textit{p+p}$ collisions at $\sqrt{s_{NN}}$ = 200 GeV. Strong short and long range correlations are seen in central (0-10%) Au+Au collisions. The magnitude of these correlations decrease with decreasing centrality until only short range correlations are observed in 40-50% Au+Au collisions. The results are in agreement with predictions from the Dual Parton and Color Glass Condensate models.

2 data tables

FB Correlation strength for Au+Au at different centralities and p+p reactions as a function of $\Delta\eta$.

Backward-forward dispersion, $D_{bf}^{2}$ and forward-forward dispersion $D_{bf}^{2}$ for Au+Au 0-10% centrality and p+p reactions as a function of $\Delta\eta$.


Measurements of the transverse-momentum-dependent cross sections of $J/\psi$ production at mid-rapidity in proton+proton collisions at $\sqrt{s} =$ 510 and 500 GeV with the STAR detector

The STAR collaboration Adam, Jaroslav ; Adamczyk, Leszek ; Adams, Joseph ; et al.
Phys.Rev.D 100 (2019) 052009, 2019.
Inspire Record 1735184 DOI 10.17182/hepdata.105629

We present measurements of the differential production cross sections of the inclusive $J/\psi$ meson as a function of transverse momentum ($p_{T}^{J/\psi}$) using the $\mu^{+}\mu^{-}$ and $e^{+}e^{-}$ decay channels in proton+proton collisions at center-of-mass energies of 510 and 500 GeV, respectively, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The measurement from the $\mu^{+}\mu^{-}$ channel is for 0 $< p_{T}^{J/\psi} <$ 9 GeV/$c$ and rapidity range $|y^{J/\psi}| < $ 0.4, and that from the $e^{+}e^{-}$ channel is for 4 $< p_{T}^{J/\psi} <$ 20 GeV/$c$ and $|y^{J/\psi}| < $ 1.0. The $\psi(2S)$ to $J/\psi$ ratio is also measured for 4 $< p_{T}^{\rm meson} <$ 12 GeV/$c$ through the $e^{+}e^{-}$ decay channel. Model calculations, which incorporate different approaches toward the $J/\psi$ production mechanism, are compared with experimental results and show reasonable agreement within uncertainties. A more discriminating comparison to theoretical models at low $p_T$ can be performed in the future, if the calculations are carried out within our fiducial volume, eliminating the uncertainty due to the $J/\psi$ polarization.

7 data tables

'fiducial cross sections multiplied by the branching ratio as a function of $J/\Psi$ $p_T$'

'full cross sections multiplied by the branching ratio as a function of $J/\Psi$ $p_T$ '

'fiducial cross sections multiplied by the branching ratio as a function of $J/\Psi$ $p_T$ '

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Transverse spin transfer to $\Lambda$ and $\bar{\Lambda}$ hyperons in polarized proton-proton collisions at $\sqrt{s}=200\,\mathrm{GeV}$

The STAR collaboration Adam, J. ; Adamczyk, Leszek ; Adams, Joseph ; et al.
Phys.Rev.D 98 (2018) 091103, 2018.
Inspire Record 1691271 DOI 10.17182/hepdata.105628

The transverse spin transfer from polarized protons to $\Lambda$ and $\bar{\Lambda}$ hyperons is expected to provide sensitivity to the transversity distribution of the nucleon and to the transversely polarized fragmentation functions. We report the first measurement of the transverse spin transfer to $\Lambda$ and $\bar{\Lambda}$ along the polarization direction of the fragmenting quark, $D_\mathrm{TT}$, in transversely polarized proton-proton collisions at $\sqrt{s}=200\,\mathrm{GeV}$ with the STAR detector at RHIC. The data correspond to an integrated luminosity of $18\,\mathrm{pb}^{-1}$ and cover the pseudorapidity range $\left|\eta\right| < 1.2$ and transverse momenta $p_{\mathrm{T}}$ up to $8\,\mathrm{GeV}/c$. The dependence on $p_\mathrm{T}$ and $\eta$ are presented. The $D_\mathrm{TT}$ results are found to be comparable with a model prediction, and are also consistent with zero within uncertainties.

7 data tables

'Transverse spin transfer of $\Lambda$ in transversely polarized proton-proton collisions at 200 GeV.'

'Transverse spin transfer of $\bar{\Lambda}$ in transversely polarized proton-proton collisions at 200 GeV.'

'spin asymmetry $\delta_{TT}$ for the control sample of $K_S^0$ meson.'

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Search for resonances decaying into photon pairs in 139 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} =$ 13 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abbott, Dale Charles ; et al.
CERN-EP-2020-248, 2021.
Inspire Record 1849059 DOI 10.17182/hepdata.100161

Searches for new resonances in the diphoton final state, with spin 0 as predicted by theories with an extended Higgs sector and with spin 2 using a warped extra-dimension benchmark model, are presented using 139 fb$^{-1}$ of $\sqrt{s} = $ 13 TeV $pp$ collision data collected by the ATLAS experiment at the LHC. No significant deviation from the Standard Model is observed and upper limits are placed on the production cross-section times branching ratio to two photons as a function of the resonance mass.

16 data tables

The expected and observed upper limits at 95\% CL on the fiducial cross-section times branching ratio to two photons of a narrow-width (Γ_X = 4 MeV) spin-0 resonance as a function of its mass m_X. For masses greater than 1000 GeV, pseudo-experiments are used to verify the expected and observed limits, and used in place of the asymptotic limit when differences are observed.

The expected and observed upper limits at 95\% CL on the production cross-section times branching ratio to two photons of the lightest KK graviton as a function of its mass for k/Mpl=0.10. For masses greater than 1000 GeV, pseudo-experiments are used to verify the expected and observed limits, and used in place of the asymptotic limit when differences are observed.

Expected and observed limits computed using asymptotic formulas as a function of the signal mass m_{X} and the relative width $\Gamma_{X}/m_{X}$ for the spin-0 resonance search.

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Search for Higgs boson production in association with a high-energy photon via vector-boson fusion with decay into bottom quark pairs at $\sqrt{s}$=13 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abbott, Dale Charles ; et al.
JHEP 03 (2021) 268, 2021.
Inspire Record 1826521 DOI 10.17182/hepdata.100160

A search is presented for the production of the Standard Model Higgs boson in association with a high-energy photon. With a focus on the vector-boson fusion process and the dominant Higgs boson decay into $b$-quark pairs, the search benefits from a large reduction of multijet background compared to more inclusive searches. Results are reported from the analysis of 132 fb$^{-1}$ of $pp$ collision data at $\sqrt{s}$=13 TeV collected with the ATLAS detector at the LHC. The measured Higgs boson signal yield in this final-state signature is $1.3 \pm 1.0$ times the Standard Model prediction. The observed significance of the Higgs boson signal above the background is 1.3 standard deviations, compared to an expected significance of 1.0 standard deviations.

13 data tables

Comparisons of data and simulated event distributions of the BDT input variable \(\Delta \eta_{jj}\) in the two \(m_{bb}\) sidebands after kinematic reweighting of the non-resonant \(b\bar{b}\gamma jj\) background. The data are shown as black points, and the background contributions are stacked in coloured histograms. The Higgs boson signal contribution is scaled up and represented by the dashed red line. The bottom panel in each plot shows the ratio of the data to the SM prediction, where the uncertainty band corresponds to the statistical uncertainty only.

Comparisons of data and simulated event distributions of the BDT input variable \(p_{\text{T}}^{\text{balance}}\) in the two \(m_{bb}\) sidebands after kinematic reweighting of the non-resonant \(b\bar{b}\gamma jj\) background. The data are shown as black points, and the background contributions are stacked in coloured histograms. The Higgs boson signal contribution is scaled up and represented by the dashed red line. The bottom panel in each plot shows the ratio of the data to the SM prediction, where the uncertainty band corresponds to the statistical uncertainty only.

The \(m_{bb}\) distributions in the HighBDT categories, overlaid with contributions from the \(H\gamma jj\) signal as well as the resonant \(Z\gamma jj\) and non-resonant \(b\bar{b} \gamma jj\) background fits. The combined \(\chi^2\) per degree of freedom is \(45.2/45\). The bottom panel in each plot presents the significance of the Higgs boson signal relative to the non-resonant \(b\bar{b} \gamma jj\) background in each bin.

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Search for bottom-squark pair production in $pp$ collision events at $\sqrt{s} = 13$ TeV with hadronically decaying $\tau$-leptons, $b$-jets and missing transverse momentum using the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abbott, Dale Charles ; et al.
CERN-EP-2020-235, 2021.
Inspire Record 1851675 DOI 10.17182/hepdata.99788

A search for pair production of bottom squarks in events with hadronically decaying $\tau$-leptons, $b$-tagged jets and large missing transverse momentum is presented. The analyzed dataset is based on proton-proton collisions at $\sqrt{s}$ = 13 TeV delivered by the Large Hadron Collider and recorded by the ATLAS detector from 2015 to 2018, and corresponds to an integrated luminosity of 139 fb$^{-1}$. The observed data are compatible with the expected Standard Model background. Results are interpreted in a simplified model where each bottom squark is assumed to decay into the second-lightest neutralino $\tilde \chi_2^0$ and a bottom quark, with $\tilde \chi_2^0$ decaying into a Higgs boson and the lightest neutralino $\tilde \chi_1^0$. The search focuses on final states where at least one Higgs boson decays into a pair of hadronically decaying $\tau$-leptons. This allows the acceptance and thus the sensitivity to be significantly improved relative to the previous results at low masses of the $\tilde \chi_2^0$, where bottom-squark masses up to 850 GeV are excluded at the 95% confidence level, assuming a mass difference of 130 GeV between $\tilde \chi_2^0$ and $\tilde \chi_1^0$. Model-independent upper limits are also set on the cross section of processes beyond the Standard Model.

15 data tables

The expected exclusion contour at $95\%$ CL as a function of the M(Sbottom) vs. M(N2) with the $\Delta M$(N2,N1) = 130 GeV. Masses within the contour are excluded.

The observed exclusion contour at $95\%$ CL as a function of the M(Sbottom) vs. M(N2) with the $\Delta M$(N2,N1) = 130 GeV. Masses within the contour are excluded.

Acceptance in the Single-bin SR as a function of the M(Sbottom) vs. M(N2) with the $\Delta M$(N2,N1) = 130 GeV. Keep in mind that the acceptance is given in units of $10^{-4}$.

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