123633000
The Higgs Boson Mass in MSM and the New Data
In this paper we study the implications of the top quark mass measurement at CDF for the Higgs boson mass . We find that the present data are most likely in favor of heavy Higgs boson, for , but no realistic constraints on could be derived until the measurement of reaches high precision.
43093269
Rare decays of the top quark in the one generation technicolor model.
The decays [ital t][r arrow][ital cV] ([ital V]=[gamma],[ital g],[ital Z]) and [ital t][r arrow][ital cP][sup 0] induced through loop processes are calculated in the Farhi-Susskind one family technicolor (TC) model. We find that these new contributions can enhance the SM branching fractions by as much as 3--4 orders of magnitude, i.e., [ital B]([ital t][r arrow][ital cg])[similar to]10[sup [minus]6], [ital B]([ital t][r arrow][ital cZ])[similar to]10[sup [minus]7], [ital B]([ital t][r arrow][ital c][gamma])[similar to]10[sup [minus]8], and [ital B]([ital t][r arrow][ital cP][sup 0])[similar to]10[sup [minus]9], for the favorable values of the parameters. It might provide a unique window to detect the virtual effects of pseudo Goldstone bosons in TC theory.
122968394
Multiscale technicolor and top quark decay
119099946
The Flavor-changing bottom and anti-strange quark production in the littlest Higgs model with T parity at the ILC
In the littlest Higgs model with T-parity (LHT) the mirror quarks induce the special flavor structures and some new flavor-changing (FC) couplings which could greatly enhance the production rates of the FC processes. We in this paper study some bottom and anti-strange production processes in the LHT model at the International Linear Collider (ILC), i.e., $e^+e^-\to b\bar{s}$ and $\gamma\gamma\to b\bar{s}$. The results show that the production rates of these processes are sizeable for the favorable values of the parameters. Therefore, it is quite possible to test the LHT model or make some constrains on the relevant parameters of the LHT through the detection of these processes at the ILC.
14268595
Phase transition of finite size quark droplets with isospin chemical potential in the Nambu–Jona-Lasinio model
Making use of the Nambu\char21{}Jona-Lasinio model and the multiple reflection expansion approximation, we study the phase transition of the finite size droplet with $u$ and $d$ quarks. We find that the dynamical masses of $u$, $d$ quarks are different, and the chiral symmetry can be restored at different critical radii for $u$, $d$ quarks. It provides a clue to understanding the effective nucleon mass splitting in nuclear matter. Meanwhile, it shows that the maximal isospin chemical potential at zero temperature is much smaller than the mass of pion in free space.
118036569
Detecting Toppion via a Flavor-Changing Single Top QuarkProduction Process*
In the framework of topcolor-assisted technicolor (TC2) theory, we study a flavor changing single top quarkproduction process pp(pp) →Ⅱ0t → tc(tc) at upgraded Tevatron and LHC. The results show that with the flavor changingcoupling of neutral toppion to top and charm quark, toppion provides a large te-channel resonance effect. The signal ofsingle top production could be detected at LHC. Otherwise, the narrow peak in the invariant mass distribution could beclearly detected both at upgraded Tevatron and LHC. Therefore, such single top production process provides a uniqueway to test TC2 model via the detection of tc-channel neutral toppion contribution.
119209391
Four jets as a probe of O(100 GeV) physics beyond standard model at hadron colliders
O(100 GeV) physics beyond the standard model (BSM) could be overlooked provided that it is hidden in the untouched Higgs sector or jets. The top quark forward-backward asymmetry measurements and di-jet bump, which is observed in the associated production with charged lepton plus missing energy (supposed arising from W decay), may indicate the existence of a new color-octet axial-vector Z_C with a mass about 145 GeV. Here Z_C only decays into two jets. In this paper we investigated the possibility to discover Z_C pair via analyzing the four jets as the final states, which are heavily polluted by huge QCD background. Our simulation showed that, however, both Tevatron and LHC have the excellent chance to discover Z_C through analyzing the four jets events in the current accumulated data.
59430123
Drive Laser and Optical Transport Line for Photoinjector
A Photo-Cathode RF Gun is under development at NSRL. In this paper, the drive laser system is introduced and performance parameters are presented. We adopt a BNL type gun with laser illuminating the cathode at oblique incidence. To correct “time slew” and “elliptical spot” problems arisen on the cathode, an adjustable optical transport line is designed. INTRODUCTION Drive laser system is the key component of photocathode high-brightness injector. To ensure the high quality of electron beams offered for FEL, the injector request a reliable laser with prominent performance parameters, such as: pulse duration, beam profile, energy stability, pulse to pulse stability, pointing stability and phase jitter. We adopted a BNL type gun with p-polarized laser at oblique incidence, as to acquire high quantum efficiency and low thermal emittance [1]. But, the problems of “time slew” and “elliptical spot” will arise on the cathode. To correct them, an adjustable optical transport line was designed. DRIVE LASER SYSTEM We employed a drive laser system developed by High Q Laser Production GmbH [2]. It consisted of three main parts: oscillator with a timing stabilizer, a regenerative amplifier, and the frequency conversion part. Fig.1 is the layout of the drive laser system. Figure 1: Layout of the drive laser system Oscillator The seeding laser is a passive mode-locked laser with a semiconductor absorber mirror (SESAM). Its repetition rate is 102MHz, equal to 1/28 of 2856MHz S-band radio frequency, which is used for RF-gun. The timing stabilizer measure the phase offset between laser pulses and reference RF signal,then adjust the cavity length by putting one laser resonator mirror on a voltage controlled piezo to synchronize the two signals. Regenerative Amplifier The Pockels Cell captures pulses from the continuous seeding laser and determines the pass times of pulse in the regenerative amplifier cavity. The repetition rate of amplified pulses is optional from 10 to 100Hz. Frequency Conversion Part The SHG convert the IR light (1047nm) to green light (523nm), then the FHG convert the green light to UV light (262nm). The conversion efficiency is about 20% from the fundamental to the 4-th harmonics. LASER PERFORMANCE Pulse Duration The autocorrelation measurement result of IR pulse width was 8.3ps FWHW (deconvolved value taken from the Fig.2). The UV pulse width could be close to this value. Figure 2: Pulse width @ 1047 nm measured after Regenerative Amplifier @ 10Hz Beam Profile and Diameter The beam profile and diameter of UV laser pulse was measured by a CCD camera. Beam profile was shown as Fig.3. The beam diameter in X and Y direction were 2.051mm and 1.927mm respectively, which were statistical results of 300 shots. ___________________________________________ *Work supported by the second phase of “985” project hezhg@mail.ustc.edu.cn Proceedings of IPAC’10, Kyoto, Japan TUPEA035 07 Accelerator Technology T24 Lasers 1405 Pulse to Pulse Stability The UV pulse to pulse stability was measured by a photodiode connected with an oscilloscope. The area integration was measured. The fluctuation was calculated as: σ/μ∗100%. The result was about 0.8% over two hours, as shown in Fig.4. Figure 3: Beam profile of UV laser Figure 4: Pulse stability of UV over 2h: measured with 50 Ohm feed-through-terminated input; 500 MHz Bandwidth Tektronix TDS 3052, DC-coupled) Figure 5: Pointing stability measurement Figure 6:Long term energy stability measurement results Pointing Stability Beam pointing stability was measured with a lens of 600mm focal length. The CCD camera was placed at a distance of 700mm from the lens. Pointing stability of the beam centroid were 6.13μrad rms in X direction and 19.31μrad rms in Y direction. Fig.5 showed us the measured pointing stability of centroid point and also peak point. Energy Stability The long term (over 17 hours) energy fluctuation of UV measured by an energy meter was about 0.6% rms, as shown in Fig.6. The measurement precision is dependent on resolution of energy sensor. We think the actual value is higher than the measured one. Phase Jitter The phase jitter between oscillator and reference signal (signal generator: E8257D) was measured. The output signal was presented in Fig.7. Jitter calculation as: 6 0 1 1 14.2 360 102 10 360 rms rms OSC Jitter U mV f Hz = = × ∗ × o 387 rms Jitter fs = Scaling: 1000 1 mV = o To gain a low jitter, a signal generator with low phase noise is required. Signal generators E8257D and E8663B from Agilent are suitable. All of the laser performance parameters were listed on Table 1. OPTICAL TRANSPORT LINE Because of oblique incidence design of BNL type gun, two problems of “time slew” and “elliptical spot” will arise on photo-cathode. To correct them, two prisms were used to add appropriate negative time slew and TUPEA035 Proceedings of IPAC’10, Kyoto, Japan 1406 07 Accelerator Technology T24 Lasers ellipticity on laser pulse wave front. The added time slew is: τ=f(r,α), α is the angle of prism, r is the laser diameter on the prism. A variable beam expander was used to adjust the r . Therefore, the added time slew can be adjustable. The beam diameter on cathode can be controlled by a movable lens at the end of optical line. The Y direction beam diameter was also fore-adjusted by prisms. The sketch of optical transport line was shown as Fig.8. The beam profile after the two prisms was measured by a CCD camera, which was showed in Fig.9. The X direction diameter was compressed to 1.0mm, The Y direction diameter was still about 1.9mm. To compress the Y direction diameter, one just needs to rotate the prisms. The transmission efficiency of the two prisms is about 92%. Figure 7: SYNC-phase output signal, RMS=14.2mV Figure 8: Sketch of optical transport line Figure 9: Beam profile after two prisms Table 1: The performance of drive laser system 1 Wave length/nm 262 2 Pulse duration (FWHM) /ps 8.3 3 Oscillator frequency/MHz 102 4 UV repeat rate/Hz 10-100 5 UV energy/mJ 0-0.65 6 Energy fluctuation/rms 0.6% 7 Pulse to pulse stability/rms 0.8% 8 X direction Point stability/μrad 6.13 9 Y direction Point stability/μrad 19.31 10 Phase jitter/fs 387 11 X direction beam diameter/(1/emm) 2.051 12 Y direction beam diameter/(1/emm) 1.927 SUMMARY We described the drive laser system and presented the measured laser performance parameters. We also reported a preparatory design of optical transport line used to correct “time slew” and “elliptical spot” problems. We are going to reshape the laser pulse. In the aspect of spatial shaping, a commercial production from pi-shaper [3] and GBS-UVH [4] may be considered. Both of them showed favourable shaping effects [5] [6]. In the aspect of temporal shaping, we are going to try the pulse stacking method [6] [7]. REFERENCES [1] Xiang D et al. Nuclear Instruments and Methods in Physics Research A, 2006, (562): 48-52. [2] http://www.highqlaser.at/ [3] http://www.pishaper.com/ [4] http://search.newport.com/?sku=GBS-UV-H [5] D.H. Dowell et al., Proceedings of PAC07, Albuquerque, New Mexico, USA TUPMS058. [6] A.K. Sharma, T, Tsang, and T. Rao, PHYSICAL REVIEW SPECIAL TOPICS ACCELERATORS AND BEAMS 12, 033501 (2009). [7] H. Tomizawa et al., Proceedings of FEL 2007, Novosibirsk, Russia WEBAU01. Proceedings of IPAC’10, Kyoto, Japan TUPEA035 07 Accelerator Technology T24 Lasers 1407
15077681
Enhancement of intermediate mass dileptons from charm decays at SPS energies
Abstract We study the dimuon yield from open charm decays in the intermediate mass region(IMR) in heavy-ion collisions at the CERN-SPS energy. We find that final state rescatterings which broaden the m T spectrum of charmed mesons can enrich the part of the phase space covered by the NA50 experiment, thus lead to an apparent enhancement of IMR dileptons within the acceptance of the experiment. Such an enhancement increases with the dimuon invariant mass and the single muon energy cut-off.
119118563
Transverse momentum broadening in semi-inclusive deep inelastic scattering at next-to-leading order
Within the framework of higher-twist collinear factorization, transverse momentum broadening for the final hadrons in semi-inclusive deeply inelastic $e+A$ collisions is studied at the next-to-leading order (NLO) in perturbative QCD. Through explicit calculations of real and virtual corrections at twist-4, the transverse momentum weighted differential cross section due to double scattering is shown to factorize at NLO and can be expressed as a convolution of twist-4 nuclear parton correlation functions, the usual twist-2 fragmentation functions and hard parts which are finite and free of any divergences. A QCD evolution equation is also derived for the renormalized twist-4 quark-gluon correlation function which can be applied to future phenomenological studies of transverse momentum broadening and jet quenching at NLO.
17610122
HIJING 1.0: A Monte Carlo program for parton and particle production in high-energy hadronic and nuclear collisions
Based on QCD-inspired models for multiple jets production, we developed a Monte Carlo program to study jet and the associated particle production in high energy pp, pA and AA collisions. The physics behind the program which includes multiple minijet production, soft excitation, nuclear shadowing of parton distribution functions and jet interaction in dense matter is briefly discussed. A detailed description of the program and instructions on how to use it are given.