Dr. Roberta Ferretti

13 December 2010 in Physical Review Letters

Journal Article

Elliptic Flow of Charged Particles in Pb-Pb Collisions at

\sqrt{s_{N N}} = 2.76 TeV

KA

K. Aamodt

BA

B. Abelev

AQ

A. Abrahantes Quintana

DA

D. Adamová

AA

A. M. Adare

MZ

M. Zynovyev

+953

We report the first measurement of charged particle elliptic flow in Pb-Pb collisions at

\sqrt{s_{N N}} = 2.76 TeV

with the ALICE detector at the CERN Large Hadron Collider. The measurement is performed in the central pseudorapidity region (

| η | < 0.8

) and transverse momentum range

0.2 < p_{t} < 5.0 GeV / c

. The elliptic flow signal

v_{2}

, measured using the 4-particle correlation method, averaged over transverse momentum and pseudorapidity is

0.087 \pm 0.002 (stat) \pm 0.003 (syst)

in the 40%–50% centrality class. The differential elliptic flow

v_{2} (p_{t})

reaches a maximum of 0.2 near

p_{t} = 3 GeV / c

. Compared to RHIC Au-Au collisions at

\sqrt{s_{N N}} = 200 GeV

, the elliptic flow increases by about 30%. Some hydrodynamic model predictions which include viscous corrections are in agreement with the observed increase.

14 May 2015 in The European Physical Journal C

Journal Article

Precise determination of the mass of the Higgs boson and tests of compatibility of its couplings with the standard model predictions using proton collisions at 7 and 8 $$\,\text {TeV}$$ TeV

TC

The CMS Collaboration

VK

V. Khachatryan

AS

A. M. Sirunyan

AT

A. Tumasyan

WA

W. Adam

VR

V. Roinishvili

+2126

Properties of the Higgs boson with mass near 125

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GeV

are measured in proton-proton collisions with the CMS experiment at the LHC. Comprehensive sets of production and decay measurements are combined. The decay channels include

\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma \gamma $$\end{document}

γ γ

,

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Z Z

,

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W W

,

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τ τ

,

\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm{b} \mathrm{b} $$\end{document}

b b

, and

\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu \mu $$\end{document}

μ μ

pairs. The data samples were collected in 2011 and 2012 and correspond to integrated luminosities of up to 5.1

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{fb}^{-1}

at 7

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TeV

and up to 19.7

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{fb}^{-1}

at 8

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TeV

. From the high-resolution

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γ γ

and

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Z Z

channels, the mass of the Higgs boson is determined to be

\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$125.02\,^{+0.26}_{-0.27} \,\text {(stat)} \,^{+0.14}_{-0.15} \,\text {(syst)} \,\text {GeV} $$\end{document}

125.02_{- 0.27}^{+ 0.26} (stat)_{- 0.15}^{+ 0.14} (syst) GeV

. For this mass value, the event yields obtained in the different analyses tagging specific decay channels and production mechanisms are consistent with those expected for the standard model Higgs boson. The combined best-fit signal relative to the standard model expectation is

\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1.00\,\pm 0.09\,\text {(stat)} \,^{+0.08}_{-0.07}\,\text {(theo)} \,\pm 0.07\,\text {(syst)} $$\end{document}

1.00 \pm 0.09 (stat)_{- 0.07}^{+ 0.08} (theo) \pm 0.07 (syst)

at the measured mass. The couplings of the Higgs boson are probed for deviations in magnitude from the standard model predictions in multiple ways, including searches for invisible and undetected decays. No significant deviations are found.

11 July 2011 in Physical Review Letters

Journal Article

Higher Harmonic Anisotropic Flow Measurements of Charged Particles in Pb-Pb Collisions at

\sqrt{s_{N N}} = 2.76 TeV

KA

K. Aamodt

BA

B. Abelev

AQ

A. Abrahantes Quintana

DA

D. Adamová

AA

A. M. Adare

MZ

M. Zynovyev

+933

We report on the first measurement of the triangular

v_{3}

, quadrangular

v_{4}

, and pentagonal

v_{5}

charged particle flow in Pb-Pb collisions at

\sqrt{s_{NN}} = 2.76 TeV

measured with the ALICE detector at the CERN Large Hadron Collider. We show that the triangular flow can be described in terms of the initial spatial anisotropy and its fluctuations, which provides strong constraints on its origin. In the most central events, where the elliptic flow

v_{2}

and

v_{3}

have similar magnitude, a double peaked structure in the two-particle azimuthal correlations is observed, which is often interpreted as a Mach cone response to fast partons. We show that this structure can be naturally explained from the measured anisotropic flow Fourier coefficients.

20 January 2011 in Physical Review Letters

Journal Article

Centrality Dependence of the Charged-Particle Multiplicity Density at Midrapidity in Pb-Pb Collisions at

\sqrt{s_{NN}} = 2.76 TeV

KA

K. Aamodt

AQ

A. Abrahantes Quintana

DA

D. Adamová

AA

A. M. Adare

MA

M. M. Aggarwal

AC

ALICE Collaboration

+906

The centrality dependence of the charged-particle multiplicity density at midrapidity in Pb-Pb collisions at

\sqrt{s_{NN}} = 2.76 TeV

is presented. The charged-particle density normalized per participating nucleon pair increases by about a factor of 2 from peripheral (70%–80%) to central (0%–5%) collisions. The centrality dependence is found to be similar to that observed at lower collision energies. The data are compared with models based on different mechanisms for particle production in nuclear collisions.

1 January 2011 in Physics Letters B

Journal Article

Suppression of charged particle production at large transverse momentum in central Pb–Pb collisions at

\sqrt{s_{NN}} = 2.76 TeV

KA

K. Aamodt

AQ

A. Abrahantes Quintana

DA

D. Adamová

AA

A.M. Adare

MA

M.M. Aggarwal

MZ

M. Zynovyev

+900

Inclusive transverse momentum spectra of primary charged particles in Pb–Pb collisions at sNN=2.76 TeV have been measured by the ALICE Collaboration at the LHC. The data are presented for central and peripheral collisions, corresponding to 0–5% and 70–80% of the hadronic Pb–Pb cross section. The measured charged particle spectra in |η|<0.8 and 0.3

14 May 2014 in Physical Review D

Journal Article

Measurement of the properties of a Higgs boson in the four-lepton final state

SC

S. Chatrchyan

VK

V. Khachatryan

AS

A. M. Sirunyan

AT

A. Tumasyan

WA

W. Adam

(C

(CMS Collaboration)

+2169

The properties of a Higgs boson candidate are measured in the

H \to Z Z \to 4 ℓ

decay channel, with

ℓ = e

,

μ

, using data from

p p

collisions corresponding to an integrated luminosity of

5.1 {fb}^{- 1}

at the center-of-mass energy of

\sqrt{s} = 7 TeV

and

19.7 {fb}^{- 1}

at

\sqrt{s} = 8 TeV

, recorded with the CMS detector at the LHC. The new boson is observed as a narrow resonance with a local significance of 6.8 standard deviations, a measured mass of

125.6 \pm 0.4 (stat) \pm 0.2 (syst) GeV

, and a total width

\leq 3.4 GeV

at the 95% confidence level. The production cross section of the new boson times its branching fraction to four leptons is measured to be

{0.93}_{- 0.23}^{+ 0.26} {(stat)}_{- 0.09}^{+ 0.13} (syst)

times that predicted by the standard model. Its spin-parity properties are found to be consistent with the expectations for the standard-model Higgs boson. The hypotheses of a pseudoscalar and all tested spin-1 boson hypotheses are excluded at the 99% confidence level or higher. All tested spin-2 boson hypotheses are excluded at the 95% confidence level or higher.

Dr. Roberta Ferretti

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