From identical S- and P-wave pT/M spectra to maximally distinct polarizations: probing NRQCD with chi states

A global analysis of ATLAS and CMS measurements reveals that, at mid-rapidity, the directly-produced $\chi_{c1}$, $\chi_{c2}$ and J/$\psi$ mesons have differential cross sections of seemingly identical shapes, when presented as a function of the mass-rescaled transverse momentum, $p_{\rm T}/M$. This identity of kinematic behaviours among S- and P-wave quarkonia is certainly not a natural expectation of non-relativistic QCD (NRQCD), where each quarkonium state is supposed to reflect a specific family of elementary production processes, of significantly different $p_{\rm T}$-differential cross sections. Remarkably, accurate kinematic cancellations among the variegated NRQCD terms (colour singlets and octets) of its factorization expansion can lead to a surprisingly good description of the data. This peculiar tuning of the NRQCD mixtures leads to a clear prediction regarding the $\chi_{c1}$ and $\chi_{c2}$ polarizations, the only observables not yet measured: they should be almost maximally different from one another, and from the J/$\psi$ polarization, a striking exception in the global panorama of quarkonium production. Measurements of the difference between the $\chi_{c1}$, $\chi_{c2}$ and J/$\psi$ polarizations, complementing the observed identity of momentum dependences, represent a decisive probe of NRQCD.Comment: Submitted to European Physical Journal

Muon reconstruction and identification in CMS Run I and towards Run II

The performance of the muon reconstruction and identification in the CMS experiment at the LHC has been studied on data collected in pp collisions at $\sqrt{s} =$ 7 and 8~TeV. Results from the measurements of the muon identification efficiencies, hadron misidentification probabilities as well as the muon momentum scale and resolution are presented

Measurements of heavy flavor properties at ATLAS and CMS

The ATLAS and CMS experiments at the LHC have a rich program in heavy flavor physics and cover a variety of topics in this field. This paper presents the following recent results: The measurement of the parity-violating decay asymmetry parameter $\alpha_{b}$ in $\Lambda_{b}^0$ decays conducted by ATLAS; studies of the $B_{c}^{\pm}$ meson performed by ATLAS and CMS; and the determination of quarkonium polarization by CMS. All measurements are based on data collected in pp collisions at $\sqrt{s} = 7$~TeV

Quarkonium production measurements and searches for exotic quarkonia at CMS

The CMS experiment at the LHC studies conventional and exotic quarkonia. CMS measured the quarkonium polarization of prompt $\Psi$(nS) and $\Upsilon$(nS) states, using 2011 data taken in pp collisions at $\sqrt{s} = 7$~TeV. No strong polarization was observed in any of the states. The prompt $\Psi$(nS) differential production cross section was determined up to and even beyond 100~GeV. The production of X(3872) in its decay to J/$\psi \pi^+ \pi^-$ was also measured, using data taken in pp collisions at $\sqrt{s} = 7$~TeV. The cross section times the branching fraction of the X(3872) relative to the one of $\psi$(2S) and the fraction of X(3872) originating from B decays were determined. The prompt X(3872) differential cross section times branching fraction as a function of p$_{\mathrm T}$ was extracted. Furthermore, a search for the exotic quarkonium X$_{\mathrm b}$, decaying to $\Upsilon$(1S) $\pi^+ \pi^-$ in the mass range of 10 to 11~GeV, was conducted using data collected in pp collisions at $\sqrt{s} = 8$~TeV. No evidence of a X$_{\mathrm b}$ signal was observed. An upper limit on the relative inclusive production cross section times branching ratio of the X$_{\mathrm b}$ and $\Upsilon$(2S) states at was set

Measurements of Quarkonium production and polarization at CMS

Studies of quarkonium production and polarization play an important role in understanding QCD. CMS has recently measured the $\Upsilon$(nS) (n=1,2,3) production cross sections and polarizations, as well as the prompt $\psi$(nS) (n=1,2) polarizations, using a dimuon sample collected in proton-proton collisions in 2011 at $\sqrt{s} =$ 7 TeV. The differential cross sections of the $\Upsilon$(nS) states are presented as a function of dimuon transverse momentum, covering a wide range of $p_\mathrm{T}$ (10--100 GeV). All three states show a similar behaviour and display a change of shape from an exponential to a power-law at $p_\mathrm{T} \approx$ 20 GeV. The polarizations of the $\Upsilon$(nS) and $\psi$(nS) states are determined in bins of dimuon transverse momentum and rapidity, significantly extending the $p_\mathrm{T}$ and rapidity ranges probed by previous experiments. The experimental measurements are in disagreement with current theoretical predictions

Measurements of prompt J/ψJ/\psi and ψ(2S)\psi(2S) production and polarization at CMS

Quarkonia, bound states of a heavy quark and its antiquark, are theideal probe to study how quarks form bound states via strong interactions. Non Relativistic QuantumChromoDynamics (NRQCD) is aQCD inspired model that factorizes the production of a bound stateinto two steps: the creation of the initial quark-antiquark pair andthe transformation of the initial pair to a bound state. The NRQCDfactorization approach relies on experimental data to describe thenon-perturbative evolution of the initial pair to a bound state.This thesis describes the measurements of the production cross sections and polarizations of the prompt J/ψ and ψ(2S) mesons, whichare c¯ states that are produced either directly or via the decay ofca short-lived intermediate state. The measurements are based on adimuon data sample collected by the CMS experiment at the LHC√in proton-proton collisions at s = 7 TeV, corresponding to a total integrated luminosity of 4.9 fb−1 . The prompt J/ψ and ψ(2S)production cross sections are determined in four equidistant rapidityranges as well as over a wider integrated rapidity interval of |y| < 1.2.Four different polarization (preferred spin alignment) scenarios areconsidered. The cross sections have been measured up to transversemomenta, pT , of 120 GeV and 100 GeV for the J/ψ and ψ(2S), respectively, thereby tremendously extending the pT reach of previousCMS measurements. Moreover, the ratio of ψ(2S) to J/ψ cross sections was explicitly determined.Polarization is always measured with respect to a reference frame.The polarizations of the prompt J/ψ and ψ(2S) mesons are determined in three reference frames (HX, CS, PX) as functions of pTand |y|. In addition, a frame-invariant approach is applied. Theresults are obtained in two (three) rapidity bins and extend up topT = 70 (50) GeV in case of the J/ψ (ψ(2S)). The measured polarization values are close to zero, showing no evidence of any strongpolarization. This is in disagreement with existing NRQCD calculations that predict strong transverse polarization, especially at highpT values.The quarkonium results provided by CMS have significantly contributed to improve the understanding of hadron formation, especially because they probe the theoretical calculations in a kinematicregion where NRQCD factorization is believed to be most reliable

Quarkonium and heavy flavour production in Run I and first results with 13 TeV data at CMS

This work presents results on quarkonium and heavy flavour production using data collected by the CMS experiment at the LHC in pp collisions during Run I. The emphasis is placed on the most recent measurements, including the S-wave cross sections up to transverse momenta exceeding 100 GeV, the polarizations of $\Upsilon$(nS) mesons as function of charged particle multiplicity as well as the study of $B_c^+$ mesons decaying to $\rm{J}/\psi \pi^+$ and $\rm{J}/\psi \pi^+\pi^+ \pi^-$. Moreover, preliminary dimuon mass distributions obtained with early Run II data collected at $\sqrt{s} =$ 13 TeV in 2015 are shown

Υ\Upsilon(nS) Polarization Results Summary from CMS and CDF

Studies of heavy quarkonium production and polarization play an important role in the understanding of quantum chromodynamics (QCD). The CMS and CDF $\Upsilon$(nS) polarization analyses are the most comprehensive measurements of quarkonium polarization made so far. The three frame-dependent polarization parameters, $\lambda_{\vartheta}$, $\lambda_{\varphi}$, and $\lambda_{\vartheta\varphi}$, plus the frame-invariant parameter $\tilde\lambda$ are measured in different reference frames as a function of transverse momentum. The results of the two experiments are in good agreement. The polarization parameters are small in the reference frames under study, excluding large transverse or longitudinal polarizations, especially for the $\Upsilon$(3S) state, which is less affected by feed-down contributions with unknown polarization. These observations are in disagreement with the available theoretical expectations for high-energy hadron collisions

Υ\Upsilon(nS) Polarization in pp Collisions at the LHC with the CMS Experiment

The polarizations of the $\Upsilon$(1S), $\Upsilon$(2S) and $\Upsilon$(3S) mesons produced in proton-proton collisions at $\sqrt{s} = 7 \, \mathrm{TeV}$ are measured using a data sample collected with the CMS detector in 2011. The data correspond to an integrated luminosity of $4.9 \, \mathrm{fb^{-1}}$. The measurements are based on the analysis of the dimuon decay angular distributions, analyzed in three different polarization frames, and are presented as a function of the $\Upsilon$ transverse momentum in two rapidity ranges. The measurement of the polarization parameters, $\lambda_{\theta}, \, \lambda_{\phi}$ and $\lambda_{\theta \phi}$, is complemented by the determination of the frame-invariant quantity $\tilde{\lambda}$, which provides a useful intrinsic test of the reliability of the whole analysis chain as well as supplementary physical information. The polarization of the three $\Upsilon$ states are found to be small in the considered kinematic region ($10 < p_T < 50$~GeV, $\mid y \mid \, < 1.2$) in all the polarization frames

Black polymers in bulk - heterojunction solar cells

The active materials in polymer solar cells have a decisive role on the performance of the cells. Polymers with extended absorption, i.e., black polymers with absorption covering the whole visible region are desired in order to capture the important parts of the solar irradiation. Different ways of achieving black active materials are discussed and two new alternating polyfluorene (APFO) copolymers with broad absorption, APFO-Black 1 and APFO-Black 2, using two different design strategies are described. The UV-Vis absorption spectra of the polymers extend to approximately 850 nm, and the polymers were used as donors and [6,6]- phenyl-C6 1 -butyric acid methyl ester (PCBM)[60] or PCBM[70] as acceptors in solar cell devices in various mixing ratios. The best combinations yielded an overall power conversion efficiency of 1.2% for APFO-Black 1 and 1.5% for APFO-Black 2