abstract

Selected experimental results related to heavy-ion physics, obtained using the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC), are presented. Measurements have been performed for lead–lead (PbPb), proton–lead ($p$Pb) and proton–proton ($pp$) data samples collected in the years 2010–2012. The jet-quenching phenomenon has been studied by looking at the production of the so-called “hard probes”, such as high transverse momentum charged particles, isolated photons, $Z$ and $W$ bosons, and jets. In addition, the suppression of quarkonium states and long-range two-particle correlations have been investigated.

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A dedicated tau reconstruction algorithm developed by the CMS Collaboration is presented in detail with results of the reconstruction performance analysis. Two different tau isolation methods used by the algorithm are discussed and compared.

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The LHCb experiment has successfully taken data during the last three years. Here, results are presented for $W$, $Z$ and low mass Drell–Yan production in the forward region at LHCb. Analyses based on data collected in 2010 and 2011 are presented. The results are generally in agreement with theoretical predictions.

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In this conference paper selected results on: quantum chromodynamics jets, electroweak vector bosons, top quark and $b$-hadron production are reported. The proton–proton collision data at the centre-of-mass energies of 7 TeV and 8 TeV were collected with the Compact Muon Solenoid detector at the LHC. No deviations from predictions of the Standard Model theory of particle interactions were observed after analysing data corresponding to an integrated luminosity of up to 5 fb${}^{-1}$ at each energy.

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We examine maximum enhancement that can be achieved in the $ZZ$ and $\gamma \gamma$ channels for a two-Higgs-doublet model Higgs boson with a mass near 125 GeV. Theoretical constraints restrict substantially the possibilities for enhancing the $gg\to h\to \gamma \gamma$ or $gg\to H\to \gamma \gamma$ signal relative to that for the SM Higgs. We find enhanced rates in the $\gamma \gamma$ final state for the $h$ in the Type I 2HDM — the largest $[gg\to h\to \gamma \gamma ]$/$[gg\to h_{\mathrm{S}\mathrm{M}}\gamma \gamma ]$ ratio found is of the order of $\sim 1.3$, when $\tan \beta =4$ or $20$ and the charged Higgs boson has its minimal LEP-allowed value of $m_{H^{\pm }}=90$ GeV.

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The document reports the first combined measurements of the CKM angle $\gamma$ from LHCb, performed with $b$-hadron decays dominated by $b\to u$ and $b\to c$ tree-level amplitudes. Precision is achieved by averaging results from $B^{\pm }\to D{h}^{\pm }$ $(h=K,\pi )$, where $D\to h^{+}{h}^{-}$, $D\to K^{+}{\pi }^{-}$, $D\to K^{+}{\pi }^{-}{\pi }^{+}{\pi }^{-}$, and $D\to K_{\mathrm{S}}^0{h}^{+}{h}^{-}$. The measurements used data corresponding to an integrated luminosity of 1 fb${}^{-1}$ collected in 2011 by LHCb. Using only $B^{\pm }\to D{K}^{\pm }$ decays results, a best-fit value of $\gamma =({71.1}_{-15.7}^{+16.6}{)}^{\circ }$ is obtained. For the first time, information from $B^{\pm }\to D{\pi }^{\pm }$ decays is included in the combination. When these results are included, the best-fit value becomes $\gamma ={85.1}^{\circ }$ and we set confidence limits of $\gamma \in [61.8;67.8{]}^{\circ }$ or $[77.9;92.4{]}^{\circ }$ at 68% C.L. and $\gamma \in [43.8;101.5{]}^{\circ }$ at 95% C.L.

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This contribution is a summary of the main measurements performed by the LHCb Collaboration in the heavy flavour physics sector and regarding both the production and the spectroscopy. The measurements presented here use the data sample acquired by the experiment from 2010 and 2012 at a collision energy of $\sqrt{s}=7$ TeV and $\sqrt{s}=8$ TeV in the centre of mass. Outlooks for ongoing and future measurements are also given.

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In this paper, we present searches for the Standard Model Higgs boson performed by the CMS experiment using data recorded during proton–proton collisions at centre-of-mass energy of 7 and 8 TeV. Analyses performed in $WW$, $ZZ$, $b\bar{b}$, $\tau \tau$ and $\gamma \gamma$ channels are discussed. The combination of the above searches is presented.

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We describe a status of the software package Axiloop for symbolic calculations in the axial gauge. The package is dedicated to computations of the virtual components of the QCD NLO splitting functions in the collinear factorization scheme and its exclusive extension. We present some aspects of the employed technique, the structure of the package and results for the $C_{\mathrm{F}}^2$ part of the non-singlet case.

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The ATLAS physics program involving $\tau$ final states ranges from Standard Model measurements involving $W$, $Z$, and top pair production, to searches for the Higgs boson, Supersymmetry and other signatures beyond the Standard Model. In this article, an overview is presented of the Standard Model studies done in ATLAS with $\tau$ leptons in final states: cross section measurements of $W$, $Z$ and $t\overline{t}$ production and a $\tau$ polarization measurement in $W$ decays.

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Beyond Standard Model scenarios are being searched for signatures with the ATLAS detector, which is placed on the one of interaction points of the Large Hadron Collider. More than 40 results based on 7 TeV data collected in 2011 were published or submitted to papers. There are already available six publications based on 8 TeV data collected in 2012. No indications for New Physics have been found, and limits on many theories are presented in a few hundreds GeV to a few TeV scale. In this presentation, recent results of such new physics searches are presented.

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We review results of searches for physics beyond the Standard Model performed by the Compact Muon Solenoid detector at the Large Hadron Collider accelerator in proton–proton collisions at the center-of-mass energy of 7 TeV for data collected in 2011 and for the part of data at 8 TeV from 2012.

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The Balitsky–Kovchegov (BK) evolution equation in its resummed integral form is considered. We solve it numerically and compare to the unresummed BK equation formulated as an integral equation and to the solution obtained by the BKsolver package. Sensitivity of the solution to an introduced resolution parameter and initial conditions is investigated.

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We analyse the precise DIS reduced cross section data from HERA using the BGK dipole model with valence quarks. We show that it is possible to describe the HERA data very well using solely the dipole model gluon density with added valence quarks from the usual pdf’s.

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Three CMS measurements sensitive to small-$x$ QCD and multi-parton interactions are discussed: forward energy flow, inclusive cross-sections for forward jets production and inclusive to exclusive dijets production cross-sections ratios. Results are compared to predictions of various Monte Carlo models.

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I present here a selection of results reported by the ALICE experiment during the first three years of the LHC operation. The emphasis is on the soft observables and on the first data from the $p$–Pb collisions collected in a short pilot run in September 2012.

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In this paper, we present strategies and results of eight searches for exotic physics performed by the CMS experiment with 2011 and 2012 $pp$ collision data taken at LHC energy $\sqrt{s}$, respectively, 7 TeV and 8 TeV. Among them there are searches for heavy gauge bosons $W^{\prime }$ and $Z^{\prime }$, heavy neutrinos, heavy quarks, Kaluza–Klein gravitons, long-lived particles, quark and lepton compositeness, microscopic black holes and a number of exotic dijet resonances such as excited quarks.

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We briefly describe the building blocks of general-purpose Monte Carlo event generators for the full simulation of the proton–proton collisions at the LHC. Then, we present a comparison of three main Monte Carlo event generators, HERWIG, PYTHIA and SHERPA to a range of the LHC data.

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The CMS experiment carried out searches for the neutral and charged Higgs bosons of the Minimal Supersymmetric extension of the Standard Model based on data collected in 2011 at the center-of-mass energy of 7 TeV or a combination of 7 TeV and the first part of 8 TeV data taken in 2012. Results provide the most stringent MSSM limits in the tan$\beta$ versus $M_A$ plane to date, and severely constrain the allowed MSSM parameter space.

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In this report, results of femtoscopic analyses with ${\pi }^{\pm }{\pi }^{\pm }$, $K_{\mathrm{S}}^0{K}_{\mathrm{S}}^0$, $K^{\pm }{K}^{\pm }$, $pp$, $\overline{p}\overline{p}$, $p\overline{p}$, $\overline{p}\Lambda$ and $p\overline{\Lambda }$ in Pb–Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV registered by ALICE at the LHC are presented and compared with results from $pp$ collisions at $\sqrt{s}=7$ TeV, where available. Results from heavy-ion collisions are compatible with the hydrodynamic prediction of the scaling of the $\pi$, $K$ and $p$ emission source sizes with the transverse mass. We also show that the femtoscopic radii scale linearly with the cube root of charged particle density. The scaling parameters in Pb–Pb and $pp$ collisions are clearly different which indicates that the initial state influences the size at freeze-out. Moreover, baryon–antibaryon correlations are investigated in the context of smaller baryon yields measured in ALICE compared to the predictions of thermal models. New possible applications of femtoscopy are introduced, namely the measurements of poorly known interaction potentials (e.g. $p\overline{\Lambda }$).

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The main goals of the Absolute Luminosity For ATLAS (ALFA) detector are to provide an absolute luminosity and total cross section measurement. The measurement method used, the detector alignment and the quality of the collected data are discussed.

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An overview is presented of the developments in fixed-order calculations for hard scattering cross sections over the last one and a half decade.

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Last year a new particle with the mas of $\sim$ 125 GeV and decaying into $ZZ$, $WW$ and $\gamma \gamma$ pairs was discovered at the LHC. The evidence of the decays to fermions is still to be established. The measurement of its basic properties such as spin, parity, branching ratios are important for validation that the discovered particle is indeed the Standard Model Higgs. Such observables require not only experimental effort to understand detector performance. Precision evaluation of known physics dynamic for the processes to be measured and their backgrounds is to be completed as well. In the present paper, we will adress a part of this technical subject using as an example some of the activities performed in our theory group in Kraków. As a consequence, we will limit ourselves to simulation tools for the Higgs boson observables involving $\tau$ decays and to effect of QED bremsstrahlung in decays of $W$ and $Z$ bosons important for the background estimations. Discussion of observables for precision measurement of the $W$ boson mass important together with the top-quark and Higgs boson mass for consistency test of the Standard Model, represents complementary subject covered in this presentation. More specifically, status and applications of $\tau$ lepton decay Monte Carlo generator TAUOLA with its interfaces enabling study of heavy boson spin, will be revieved. Generator PHOTOS for bremsstrahlung in decays will be presented together with its major applications.

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Searches for electro-weak production of supersymmetry with multiple leptons in the final state are presented. The analyses use proton–proton collision data provided by the LHC and recorded with the ATLAS detector at the centre-of-mass energy of $\sqrt{s}=7$ TeV in 2011 and 8 TeV in 2012. Final states with exactly two leptons, exactly three leptons or at least four leptons are studied.

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In this paper, I present Standard Model electroweak results obtained by the CMS Collaboration after nearly 3 years of data taking. Selected measurements are discussed concerning single- and di-boson $W$/$Z$ production in proton–proton collisions at the center-of-mass of 7 and 8 TeV. Results for data are compared to predictions of various Monte Carlo models.

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During the operation in the years 2009–2013, the Large Hadron Collider (LHC) was delivering not only collisions of proton beams, but also Pb+Pb collisions and $p$+Pb collisions, at the center of mass energy $\sqrt{s_{{}_{NN}}}=2.76$ TeV and $\sqrt{s_{{}_{NN}}}=5.02$ TeV, respectively. In this contribution, selected recent results of the analyzes of heavy ion collisions from the ATLAS experiment are presented.

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Since the start of the Large Hadron Collider (LHC) the ATLAS experiment has collected data from $p+p$, Pb+Pb, and recently $p+$Pb collisions. In this paper, two topics from the heavy ion programme are presented: the study of multiplicity of produced charged particles in Pb+Pb collisions and analysis of two-particle correlations in $p+$Pb interactions. In the first case, the dependence of particle production on collision centrality is examined. The second study of $p+$Pb collisions reveals long-range pseudorapidity correlations. These correlations for particles with $|\mathrm{\Delta }\eta |>2$ are stronger for more central collisions. Subtraction of the recoil contribution, present in the most peripheral collisions, from correlations measured for more central events discloses a quadrupole-like modulation in the azimuthal angle.