New physics beyond the Standard Model could well preferentially show up at the LHC in final states with taus. The development of efficient and accurate reconstruction and identification of taus is therefore an important item in the CMS physics programme. The potentially superior performance of a particle-flow approach can help to achieve this goal with the CMS detector. Preliminary strategies are presented in this summary for the hadronic decays of the taus.
Bose-Einstein correlations of pairs of identical charged pions produced in hadronic Z decays are analyzed in terms of various parametrizations. A good description is achieved using a Levy stable distribution in conjunction with a hadronization model having highly correlated configuration and momentum space, the tau-model. Using these results, the source function is reconstructed.
The CMS experiment uses missing E_T to both measure processes in the Standard Model and test models of physics beyond the Standard Model. These proceedings show the performance of the missing E_T reconstruction evaluated by using 4.6 fb-1 of proton-proton collision data at the center-of-mass energy 7 TeV collected in 2011 with the CMS detector at the Large Hadron Collider. Missing E_T was reconstructed based on a particle-flow technique. Jet energy corrections were propagated to missing E_T. After anomalous signals and events were addressed, the missing E_T spectrum was well reproduced by MC simulation. The multiple proton-proton interactions in a single bunch crossing, pile-up events, degraded the performance of the missing E_T reconstruction. Mitigations of this degradation have been developed.
We derive a new method to improve the statistics of identified particles at high transverse momentum (pt) using online-triggered events by the Barrel Electro-Magnetic-Calorimeter (BEMC) detector. The BEMC is used to select hadronic interaction and energy deposit from showers created by charged hadrons ($pi^{pm},K^{pm}$ and $p$($bar{p}$)) in the BEMC. With this trigger, the statistics of the high pt particles are significantly enhanced by about a factor of 100 with selection efficiency up to 20%. In addition, resonant states ($rho^0$, $K^{star}$) and weak-decay V0 (Ks and La(aLa)) can be constructed by selecting the BEMC-trigger hadron as one of its daughters. We also show that the trigger efficiency can be obtained reliably in simulation and data-driven approaches.
The BESIII experiment has collected the $e^+e^-$ collision data samples corresponding to integrated luminosities of 2.93 $mathrm{fb}^{-1}$, $3.19$ $mathrm{fb}^{-1}$, 3.13 $mathrm{fb}^{-1}$ and 567 $mathrm{pb}^{-1}$ at center-of-mass energies of 3.773 GeV, 4.178 GeV, 4.189-4.226 GeV and 4.599 GeV, respectively. We report the measurements of strong-phase parameters based on the decays $D^0to K^0_{S/L}pi^+pi^-$, $D^0to K^0_{S/L}K^+K^-$, $D^0to K^-pi^+pi^+pi^-$ and $D^0to K^-pi^+pi^0$, which are important input for binned model-independent measurement of the CKM angle $gamma/phi_3$. In addition, we report amplitude analyses and branching fraction measurements of $D^+$, $D_s^+$ and $Lambda_c^+$ decays along with the $Lambda_c^+$ spin determination.
We present a method for studying the detection of jets in high energy hadronic collisions using multiplicity detector in forward rapidities. Such a study enhances the physics scope of multiplicity detectors at forward rapidities in LHC. At LHC energies the jets may be produced with significant cross section in forward rapidities. A multi resolution wavelet analysis technique can locate the spatial position of jets due to its feature of space-scale locality. The discrete wavelet proves to be very effective in probing physics simultaneously at different locations in phase space and at different scales to identify jet-like events. The key feature this analysis exploits is the difference in particle density in localized regions of the detector due to jet-like and underlying events. We find that this method has a significant sensitivity towards detecting jet position and its size. The jets can be found with the efficiency and purity of the order of 46%.