~Adler, S.S.
Max results
Sort by Reverse order

Showing 10 of 1112 results

Date

First Measurement of the Cross Section for Top-Quark Pair Production in Proton-Proton Collisions at sqrt(s)=7 TeV

The CMS collaboration Khachatryan, Vardan ; Sirunyan, Albert M. ; Tumasyan, Armen ; et al.
Phys.Lett.B 695 (2011) 424-443, 2011.
Inspire Record 874738 DOI 10.17182/hepdata.63811

The first measurement of the cross section for top-quark pair production in pp collisions at the LHC at center-of-mass energy sqrt(s)= 7 TeV has been performed using 3.1 {\pm} 0.3 inverse pb of data recorded by the CMS detector. This result utilizes the final state with two isolated, highly energetic charged leptons, large missing transverse energy, and two or more jets. Backgrounds from Drell-Yan and non-W/Z boson production are estimated from data. Eleven events are observed in the data with 2.1 {\pm} 1.0 events expected from background. The measured cross section is 194 {\pm} 72 (stat.) {\pm} 24 (syst.) {\pm} 21 (lumi.) pb, consistent with next-to-leading order predictions.

1 data table
Table 1

Total cross section. The second systematic error represents the uncertainty on the luminosity.


Search for Dijet Resonances in 7 TeV pp Collisions at CMS

The CMS collaboration Khachatryan, Vardan ; Sirunyan, Albert M. ; Tumasyan, Armen ; et al.
Phys.Rev.Lett. 105 (2010) 211801, 2010.
Inspire Record 871540 DOI 10.17182/hepdata.56737

A search for narrow resonances in the dijet mass spectrum is performed using data corresponding to an integrated luminosity of 2.9 inverse pb collected by the CMS experiment at the LHC. Upper limits at the 95% confidence level (CL) are presented on the product of the resonance cross section, branching fraction into dijets, and acceptance, separately for decays into quark-quark, quark-gluon, or gluon-gluon pairs. The data exclude new particles predicted in the following models at the 95% CL: string resonances, with mass less than 2.50 TeV, excited quarks, with mass less than 1.58 TeV, and axigluons, colorons, and E_6 diquarks, in specific mass intervals. This extends previously published limits on these models.

2 data tables
Table 1

Dijet mass spectrum. As this data is uncorrected for detector effects it is not tabulated here.

Table 2

95% CL upper limits for dijet resonances for an acceptance value (A) of 0.6.


Measurements of Dihadron Correlations Relative to the Event Plane in Au+Au Collisions at $\sqrt{s_{NN}}=200$ GeV

The STAR collaboration Agakishiev, H. ; Aggarwal, M.M. ; Ahammed, Z. ; et al.
Chin.Phys.C 45 (2021) 044002, 2021.
Inspire Record 872067 DOI 10.17182/hepdata.102351

Dihadron azimuthal correlations containing a high transverse momentum ($p_T$) trigger particle are sensitive to the properties of the nuclear medium created at RHIC through the strong interactions occurring between the traversing parton and the medium, i.e. jet-quenching. Previous measurements revealed a strong modification to dihadron azimuthal correlations in Au+Au collisions with respect to p+p and d+Au collisions. The modification increases with the collision centrality, suggesting a path-length or energy density dependence to the jet-quenching effect. This paper reports STAR measurements of dihadron azimuthal correlations in mid-central (20-60%) Au+Au collisions at $\sqrt{s_{_{\rm NN}}}=200$ GeV as a function of the trigger particle's azimuthal angle relative to the event plane, $\phi_s=|\phi_t-\psi_{\rm EP}|$. The azimuthal correlation is studied as a function of both the trigger and associated particle $p_T$. The subtractions of the combinatorial background and anisotropic flow, assuming Zero Yield At Minimum (ZYAM), are described. The correlation results are first discussed with subtraction of the even harmonic (elliptic and quadrangular) flow backgrounds. The away-side correlation is strongly modified, and the modification varies with $\phi_s$, with a double-peak structure for out-of-plane trigger particles. The near-side ridge (long range pseudo-rapidity $\Delta\eta$ correlation) appears to drop with increasing $\phi_s$ while the jet-like component remains approximately constant. The correlation functions are further studied with subtraction of odd harmonic triangular flow background arising from fluctuations. It is found that the triangular flow, while responsible for the majority of the amplitudes, is not sufficient to explain the $\phi_s$-dependence of the ridge or the away-side double-peak structure. ...

811 data tables
data table 914

background normalization systematic uncertainty band Au+Au 20-60%, 3<p_{\text{T}}^{(t)}<4 GeV/c, slice 0

data table 915

background normalization systematic uncertainty band Au+Au 20-60%, 3<p_{\text{T}}^{(t)}<4 GeV/c, slice 1

data table 916

background normalization systematic uncertainty band Au+Au 20-60%, 3<p_{\text{T}}^{(t)}<4 GeV/c, slice 2

More…

Version 2
Strange and Multi-strange Particle Production in Au+Au Collisions at $\sqrt{s_{NN}}$ = 62.4 GeV

The STAR collaboration Aggarwal, M.M. ; Ahammed, Z. ; Alakhverdyants, A.V. ; et al.
Phys.Rev.C 83 (2011) 024901, 2011.
Inspire Record 871561 DOI 10.17182/hepdata.96847

We present results on strange and multi-strange particle production in Au+Au collisions at $\sqrt{s_{NN}}=62.4$ GeV as measured with the STAR detector at RHIC. Mid-rapidity transverse momentum spectra and integrated yields of $K^{0}_{S}$, $\Lambda$, $\Xi$, $\Omega$ and their anti-particles are presented for different centrality classes. The particle yields and ratios follow a smooth energy dependence. Chemical freeze-out parameters, temperature, baryon chemical potential and strangeness saturation factor obtained from the particle yields are presented. Intermediate transverse momentum ($p_T$) phenomena are discussed based on the ratio of the measured baryon-to-meson spectra and nuclear modification factor. The centrality dependence of various measurements presented show a similar behavior as seen in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV.

0 data tables

Measurement of the parity-violating longitudinal single-spin asymmetry for $W^{\pm}$ boson production in polarized proton-proton collisions at $\sqrt{s} = 500 $GeV

The STAR collaboration Aggarwal, M.M. ; Ahammed, Z. ; Alakhverdyants, A.V. ; et al.
Phys.Rev.Lett. 106 (2011) 062002, 2011.
Inspire Record 866968 DOI 10.17182/hepdata.104930

We report the first measurement of the parity violating single-spin asymmetries for midrapidity decay positrons and electrons from $W^{+}$ and $W^{-}$ boson production in longitudinally polarized proton-proton collisions at $\sqrt{s}=500 $GeV by the STAR experiment at RHIC. The measured asymmetries, $A^{W^+}_{L}=-0.27\pm 0.10\/({\rm stat.})\pm 0.02\/({\rm syst.}) \pm 0.03\/({\rm norm.})$ and $A^{W^-}_{L}=0.14\pm 0.19\/({\rm stat.})\pm 0.02 \/({\rm syst.})\pm 0.01\/({\rm norm.})$, are consistent with theory predictions, which are large and of opposite sign. These predictions are based on polarized quark and antiquark distribution functions constrained by polarized DIS measurements.

5 data tables
Figure 3 - W-

$E^e_T$ for W+ (bottom) and W− (top) events showing the candidate histograms in black, the full background estimates in blue and the signal distributions in yellow.

Figure 3 - W+

$E^e_T$ for W+ (bottom) and W− (top) events showing the candidate histograms in black, the full background estimates in blue and the signal distributions in yellow.

Figure 4 - W-

Longitudinal single-spin asymmetry, AL, for W± events as a function of the leptonic pseudorapidity, $\eta_e$, for 25 < $E^e_T$ < 50 GeV in comparison to theory predictions

More…

Scaling properties at freeze-out in relativistic heavy ion collisions

The STAR collaboration Aggarwal, M.M. ; Ahammed, Z. ; Alakhverdyants, A.V. ; et al.
Phys.Rev.C 83 (2011) 034910, 2011.
Inspire Record 865572 DOI 10.17182/hepdata.104504

Identified charged pion, kaon, and proton spectra are used to explore the system size dependence of bulk freeze-out properties in Cu+Cu collisions at $\sqrt{s_{NN}}$=200 and 62.4 GeV. The data are studied with hydrodynamically-motivated Blast-wave and statistical model frameworks in order to characterize the freeze-out properties of the system. The dependence of freeze-out parameters on beam energy and collision centrality is discussed. Using the existing results from Au+Au and $pp$ collisions, the dependence of freeze-out parameters on the system size is also explored. This multi-dimensional systematic study furthers our understanding of the QCD phase diagram revealing the importance of the initial geometrical overlap of the colliding ions. The analysis of Cu+Cu collisions, which expands the system size dependence studies from Au+Au data with detailed measurements in the smaller system, shows that the bulk freeze-out properties of charged particles studied here scale with the total charged particle multiplicity at mid-rapidity, suggesting the relevance of initial state effects.

26 data tables
Figure 3(a)

Negatively charged pion spectra from Cu+Cu collisions 200 GeV as a function of pT for different centralities.

Figure 3(b)

Negatively charged pion spectra from Cu+Cu collisions 62.4 GeV as a function of pT for different centralities.

Figure 3(c)

Negatively charged kaon spectra from Cu+Cu collisions 200 GeV as a function of pT for different centralities.

More…

Measurement of the $t\bar{t}$ Production Cross Section with an $in$ $situ$ Calibration of $b$-jet Identification Efficiency

The CDF collaboration Aaltonen, T. ; Alvarez Gonzalez, B. ; Amerio, S. ; et al.
Phys.Rev.D 83 (2011) 071102, 2011.
Inspire Record 862617 DOI 10.17182/hepdata.56857

A measurement of the top-quark pair-production cross section in ppbar collisions at sqrt{s}=1.96 TeV using data corresponding to an integrated luminosity of 1.12/fb collected with the Collider Detector at Fermilab is presented. Decays of top-quark pairs into the final states e nu + jets and mu nu + jets are selected, and the cross section and the b-jet identification efficiency are determined using a new measurement technique which requires that the measured cross sections with exactly one and multiple identified b-quarks from the top-quark decays agree. Assuming a top-quark mass of 175 GeV/c^2, a cross section of 8.5+/-0.6(stat.)+/-0.7(syst.) pb is measured.

1 data table
Table 1

Measured cross section assuming top mass of 175 GeV.


Version 2
Measurement of the Bottom contribution to non-photonic electron production in $p+p$ collisions at $\sqrt{s} $=200 GeV

The STAR collaboration Aggarwal, M.M. ; Ahammed, Z. ; Alakhverdyants, A.V. ; et al.
Phys.Rev.Lett. 105 (2010) 202301, 2010.
Inspire Record 860571 DOI 10.17182/hepdata.101352

The contribution of $B$ meson decays to non-photonic electrons, which are mainly produced by the semi-leptonic decays of heavy flavor mesons, in $p+p$ collisions at $\sqrt{s} =$ 200 GeV has been measured using azimuthal correlations between non-photonic electrons and hadrons. The extracted $B$ decay contribution is approximately 50% at a transverse momentum of $p_{T} \geq 5$ GeV/$c$. These measurements constrain the nuclear modification factor for electrons from $B$ and $D$ meson decays. The result indicates that $B$ meson production in heavy ion collisions is also suppressed at high $p_{T}$.

3 data tables
Table 1

Distributions of the azimuthal angle between nonphotonic electrons and charged hadrons normalized per nonphotonic electron trigger. The trigger electron has (top) $2.5 < p_{T} < 3.5$ GeV/$c$ and (bottom) $5.5 < p_{T} < 6.5$ GeV/$c$. The curves represent PYTHIA calculations for $D$ (dotted curve) and $B$ (dashed curve) decays. The fit result is shown as the black solid curve.

Table 2

(a) Background-subtracted invariant mass distribution of $K$ pairs requiring at least one nonphotonic electron trigger in the event. The solid line is a Gaussian fit to the data near the peak region. (b) Distribution of the azimuthal angle between nonphotonic electron (positron) trigger particles and $D^{0}$ ($\bar{D}^{0}$). The solid (dashed) line is a fit of the correlation function from PYTHIA (MC$@$NLO) simulations to the data points.

Table 3

Transverse momentum dependence of the relative contribution from $B$ mesons ($r_{B}$) to the nonphotonic electron yields. Error bars are statistical and brackets are systematic uncertainties. The solid curve is the FONLL calculation [14]. Theoretical uncertainties are indicated by the dashed curves.


Differential cross sections and recoil polarizations for the reaction gamma p -> K+ Sigma0

The CLAS collaboration Dey, B. ; Meyer, C.A. ; Bellis, M. ; et al.
Phys.Rev.C 82 (2010) 025202, 2010.
Inspire Record 857728 DOI 10.17182/hepdata.55696

High-statistics measurements of differential cross sections and recoil polarizations for the reaction $\gamma p \rightarrow K^+ \Sigma^0$ have been obtained using the CLAS detector at Jefferson Lab. We cover center-of-mass energies ($\sqrt{s}$) from 1.69 to 2.84 GeV, with an extensive coverage in the $K^+$ production angle. Independent measurements were made using the $K^{+}p\pi^{-}$($\gamma$) and $K^{+}p$($\pi^-, \gamma$) final-state topologies, and were found to exhibit good agreement. Our differential cross sections show good agreement with earlier CLAS, SAPHIR and LEPS results, while offering better statistical precision and a 300-MeV increase in $\sqrt{s}$ coverage. Above $\sqrt{s} \approx 2.5$ GeV, $t$- and $u$-channel Regge scaling behavior can be seen at forward- and backward-angles, respectively. Our recoil polarization ($P_\Sigma$) measurements represent a substantial increase in kinematic coverage and enhanced precision over previous world data. At forward angles we find that $P_\Sigma$ is of the same magnitude but opposite sign as $P_\Lambda$, in agreement with the static SU(6) quark model prediction of $P_\Sigma \approx -P_\Lambda$. This expectation is violated in some mid- and backward-angle kinematic regimes, where $P_\Sigma$ and $P_\Lambda$ are of similar magnitudes but also have the same signs. In conjunction with several other meson photoproduction results recently published by CLAS, the present data will help constrain the partial wave analyses being performed to search for missing baryon resonances.

149 data tables
Table 1

Differential cross section as a function of COS(THETA(K+,CM)) for the centre-of mass range 1.69 to 1.7 GeV.

Table 2

Differential cross section as a function of COS(THETA(K+,CM)) for the centre-of mass range 1.7 to 1.71 GeV.

Table 3

Differential cross section as a function of COS(THETA(K+,CM)) for the centre-of mass range 1.71 to 1.72 GeV.

More…

Midrapidity antiproton-to-proton ratio in pp collisions at $\sqrt{s} = 0.9$ and $7$~TeV measured by the ALICE experiment

The ALICE collaboration Aamodt, K. ; Abel, N. ; Abeysekara, U. ; et al.
Phys.Rev.Lett. 105 (2010) 072002, 2010.
Inspire Record 859610 DOI 10.17182/hepdata.55557

The ratio of the yields of antiprotons to protons in pp collisions has been measured by the ALICE experiment at $\sqrt{s} = 0.9$ and $7$ TeV during the initial running periods of the Large Hadron Collider(LHC). The measurement covers the transverse momentum interval $0.45 < p_{\rm{t}} < 1.05$ GeV/$c$ and rapidity $|y| < 0.5$. The ratio is measured to be $R_{|y| < 0.5} = 0.957 \pm 0.006 (stat.) \pm 0.014 (syst.)$ at $0.9$ TeV and $R_{|y| < 0.5} = 0.991 \pm 0.005 (stat.) \pm 0.014 (syst.)$ at $7$ TeV and it is independent of both rapidity and transverse momentum. The results are consistent with the conventional model of baryon-number transport and set stringent limits on any additional contributions to baryon-number transfer over very large rapidity intervals in pp collisions.

2 data tables
Table 1

The PT dependence of the pbar/p ratio for the central rapidity region ABS(YRAP)<0.5.

Table 2

The central rapidity pbar/p ratio as a function of the rapidity interval Ybeam-Ybaryon and centre-of-mass energy. As well as the present ALICE measurements this table also lists the values from other experiments (see the text of the paper for details).